[analyzer] fix CHANGELOG after versioning mistake.

https://dart-review.googlesource.com/c/sdk/+/444461 deprecated
`Diagnostic.data` and added some return types to `DiagnosticReporter`
to give clients an alternative to using it. Hence, it should have been
accompanied by a minor version bump. When I sent it for review, I
failed to realize that analyzer 8.1.0 had already been released, so I
didn't do the necessary bump, and I added a note to the CHANGELOG in
the wrong place.

This change fixes the CHANGELOG. The version bump is no longer needed
since it was done in
https://dart-review.googlesource.com/c/sdk/+/444863.

Change-Id: I6a6a6964c71f5a000aa51a314f5aaef40f92a63f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/444901
Auto-Submit: Paul Berry <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: stereotype441

pkg/analyzer/CHANGELOG.md

@@ -1,4 +1,6 @@
 ## 8.2.0-dev
+* Deprecate `Diagnostic.data`. Instead, please use an expando to attach data to
+  the `Diagnostic` object.
 * Deprecate `CatchClauseParameter.declaredElement` and `CatchClauseParameter.declaredElement2`.
   Use `CatchClauseParameter.declaredFragment` instead.
 * Deprecate `DeclaredIdentifier.declaredElement` and `DeclaredIdentifier.declaredElement2`.
@@ -32,8 +34,6 @@
 * Deprecate `ClassElement.isImplementableIn`; use `isImplementableOutside` instead.
 * Deprecate `ClassElement.isMixableIn`; use `isMixableOutside` instead.
 * Deprecate `MixinElement.isImplementableIn`; use `isImplementableOutside` instead.
-* Deprecate `Diagnostic.data`. Instead, please use an expando to attach data to
-  the `Diagnostic` object.
 
 ## 8.0.0
 * Remove deprecated element model V1.