Revert xamlTools for this week's prerelease update

Revert xamlTools to what it was 2 weeks ago, to avoid the problem in
https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2429317,
with references to the wrong version of Microsoft.VisualStudio.Threading.

A proper fix will go to main, but for this week's prerelease update we're
just reverting to the xamlTools version currently shipping in prerelease.
There aren't any important fixes getting missed, so revert isn't a problem.

Author: Bret Johnson

CHANGELOG.md

@@ -4,7 +4,7 @@
 - Debug from .csproj and .sln [#5876](https://github.com/dotnet/vscode-csharp/issues/5876)
 
 # 2.72.x
-* Bump xamlTools to 17.14.35927.264 (PR: [#8100](https://github.com/dotnet/vscode-csharp/pull/8100))
+* Revert xamlTools to 17.14.35913.250 (PR: [#8100](https://github.com/dotnet/vscode-csharp/pull/8100))
 * Update Roslyn to 4.14.0-3.25178.1 (PR: [#8103](https://github.com/dotnet/vscode-csharp/pull/8103))
   * Merge `null conditional assignment` to main (PR: [#77867](https://github.com/dotnet/roslyn/pull/77867))
   * Merge `features/extensions` into `main` (PR: [#77851](https://github.com/dotnet/roslyn/pull/77851))

package.json

@@ -41,7 +41,7 @@
     "omniSharp": "1.39.12",
     "razor": "9.0.0-preview.25177.4",
     "razorOmnisharp": "7.0.0-preview.23363.1",
-    "xamlTools": "17.14.35927.264"
+    "xamlTools": "17.14.35913.250"
   },
   "main": "./dist/extension",
   "l10n": "./l10n",