cloud: update the support info of fulltext syntax (#21967)

Author: qiancai

mysql-compatibility.md

@@ -45,6 +45,11 @@ You can try out TiDB features on [TiDB Playground](https://play.tidbcloud.com/?u
 + Events
 + User-defined functions
 + `FULLTEXT` syntax and indexes [#1793](https://github.com/pingcap/tidb/issues/1793)
+
+    >**Note:**
+    >
+    > Currently, only {{{ .starter }} and {{{ .essential }}} clusters in certain AWS regions support [`FULLTEXT` syntax and indexes](https://docs.pingcap.com/tidbcloud/vector-search-full-text-search-sql). TiDB Self-Managed and TiDB Cloud Dedicated support parsing the `FULLTEXT` syntax but do not support using the `FULLTEXT` indexes.
+
 + `SPATIAL` (also known as `GIS`/`GEOMETRY`) functions, data types and indexes [#6347](https://github.com/pingcap/tidb/issues/6347)
 + Character sets other than `ascii`, `latin1`, `binary`, `utf8`, `utf8mb4`, and `gbk`.
 + Optimizer trace

sql-statements/sql-statement-add-index.md

@@ -96,7 +96,12 @@ mysql> EXPLAIN SELECT * FROM t1 WHERE c1 = 3;
 
 * TiDB accepts index types such as `HASH`, `BTREE` and `RTREE` in syntax for compatibility with MySQL, but ignores them.
 * `SPATIAL` indexes are not supported.
-* TiDB supports parsing the `FULLTEXT` syntax but does not support using the `FULLTEXT` indexes.
+* TiDB Self-Managed and TiDB Cloud Dedicated supports parsing the `FULLTEXT` syntax but does not support using the `FULLTEXT` indexes.
+
+    >**Note:**
+    >
+    > Currently, only {{{ .starter }} and {{{ .essential }}} clusters in certain AWS regions support [`FULLTEXT` syntax and indexes](https://docs.pingcap.com/tidbcloud/vector-search-full-text-search-sql).
+
 * Descending indexes are not supported (similar to MySQL 5.7).
 * Adding the primary key of the `CLUSTERED` type to a table is not supported. For more details about the primary key of the `CLUSTERED` type, refer to [clustered index](/clustered-indexes.md).
 * Setting a `PRIMARY KEY` or `UNIQUE INDEX` as a [global index](/partitioned-table.md#global-indexes) with the `GLOBAL` index option is a TiDB extension for [partitioned tables](/partitioned-table.md) and is not compatible with MySQL.

sql-statements/sql-statement-create-index.md

@@ -384,7 +384,12 @@ The system variables associated with the `CREATE INDEX` statement are `tidb_ddl_
 
 ## MySQL compatibility
 
-* TiDB supports parsing the `FULLTEXT` syntax but does not support using the `FULLTEXT`, `HASH`, and `SPATIAL` indexes.
+* TiDB Self-Managed and TiDB Cloud Dedicated support parsing the `FULLTEXT` syntax but do not support using the `FULLTEXT`, `HASH`, and `SPATIAL` indexes.
+
+    >**Note:**
+    >
+    > Currently, only {{{ .starter }} and {{{ .essential }}} clusters in certain AWS regions support [`FULLTEXT` syntax and indexes](https://docs.pingcap.com/tidbcloud/vector-search-full-text-search-sql).
+
 * TiDB accepts index types such as `HASH`, `BTREE` and `RTREE` in syntax for compatibility with MySQL, but ignores them.
 * Descending indexes are not supported (similar to MySQL 5.7).
 * Adding the primary key of the `CLUSTERED` type to a table is not supported. For more details about the primary key of the `CLUSTERED` type, refer to [clustered index](/clustered-indexes.md).

sql-statements/sql-statement-create-table.md

@@ -272,7 +272,12 @@ mysql> DESC t1;
 
 * All of the data types except spatial types are supported.
 * TiDB accepts index types such as `HASH`, `BTREE` and `RTREE` in syntax for compatibility with MySQL, but ignores them.
-* TiDB supports parsing the `FULLTEXT` syntax but does not support using the `FULLTEXT` indexes.
+* TiDB Self-Managed and TiDB Cloud Dedicated support parsing the `FULLTEXT` syntax but do not support using the `FULLTEXT` indexes.
+
+    >**Note:**
+    >
+    > Currently, only {{{ .starter }} and {{{ .essential }}} clusters in certain AWS regions support [`FULLTEXT` syntax and indexes](https://docs.pingcap.com/tidbcloud/vector-search-full-text-search-sql).
+
 * Setting a `PRIMARY KEY` or `UNIQUE INDEX` as a [global index](/partitioned-table.md#global-indexes) with the `GLOBAL` index option is a TiDB extension for [partitioned tables](/partitioned-table.md) and is not compatible with MySQL.
 
 <CustomContent platform="tidb">