Update variables.md (#33279)

In my testing, this format is needed for tag matching:
{{#is_match "host.role.name" "database_server"}}
Updated documentation accordingly.

Author: DanielYoungDude

content/en/monitors/notify/variables.md

@@ -109,7 +109,7 @@ Search for a substring in a [tag variable](#attribute-and-tag-variables) with th
 To notify your DB team if a triggering host has the tag `role:db_cassandra` or `role:db_postgres`, use the following:
 
 ```text
-{{#is_match "role.name" "db"}}
+{{#is_match "host.role.name" "db"}}
   This displays if the host triggering the alert contains `db`
   in the role name. @[email protected]
 {{/is_match}}
@@ -118,7 +118,7 @@ To notify your DB team if a triggering host has the tag `role:db_cassandra` or `
 The `is_match` condition also supports matching multiple strings:
 
 ```text
-{{#is_match "role.name" "db" "database"}}
+{{#is_match "host.role.name" "db" "database"}}
   This displays if the host triggering the alert contains `db` or `database`
   in the role name. @[email protected]
 {{/is_match}}
@@ -127,7 +127,7 @@ The `is_match` condition also supports matching multiple strings:
 To send a different notification if the tag doesn't contain `db`, use the negation of the condition as follows:
 
 ```text
-{{^is_match "role.name" "db"}}
+{{^is_match "host.role.name" "db"}}
   This displays if the role tag doesn't contain `db`.
   @slack-example
 {{/is_match}}
@@ -136,7 +136,7 @@ To send a different notification if the tag doesn't contain `db`, use the negati
 Or use the `{{else}}` parameter in the first example:
 
 ```text
-{{#is_match "role.name" "db"}}
+{{#is_match "host.role.name" "db"}}
   This displays if the host triggering the alert contains `db`
   in the role name. @[email protected]
 {{else}}