Fix outdated readme and remove outdated experimental comments (#1383)

Author: marandaneto

dart/lib/src/sentry_options.dart

@@ -71,18 +71,12 @@ class SentryOptions {
   }
 
   /// Maximum number of spans that can be attached to single transaction.
-  ///
-  /// The is an experimental feature. Use at your own risk.
   int _maxSpans = 1000;
 
   /// Returns the maximum number of spans that can be attached to single transaction.
-  ///
-  /// The is an experimental feature. Use at your own risk.
   int get maxSpans => _maxSpans;
 
   /// Sets the maximum number of spans that can be attached to single transaction.
-  ///
-  /// The is an experimental feature. Use at your own risk.
   set maxSpans(int maxSpans) {
     assert(maxSpans > 0);
     _maxSpans = maxSpans;

flutter/README.md

@@ -101,8 +101,6 @@ runApp(
 
 This adds performance tracing for all `AssetBundle` usages, where the `AssetBundle` is accessed with `DefaultAssetBunlde.of(context)`.
 This includes all of Flutters internal access of `AssetBundle`s, like `Image.asset` for example.
-Tracing for `AssetBundle.loadStructuredData()` is currently disabled.
-It's hidden by the `enableStructuredDataTracing` flag and considered experimental. Using it could lead to bugs. We recognize the irony.
 
 ##### Tracking HTTP events