Update C# Stable API delineations (#1050)

Author: jeff-allen-mongo

source/reference/stable-api.txt

@@ -125,8 +125,8 @@ application's MongoClient:
       .. literalinclude:: /driver-examples/VersionedApiExamples.cs
          :language: csharp
          :dedent: 12
-         :start-after: Start Versioned API Example 1
-         :end-before: End Versioned API Example 1
+         :start-after: Start Stable API Example 1
+         :end-before: End Stable API Example 1
 
    .. tab::
       :tabid: nodejs
@@ -281,8 +281,8 @@ Use the sample code to create a *strict* client:
       .. literalinclude:: /driver-examples/VersionedApiExamples.cs
          :language: csharp
          :dedent: 12
-         :start-after: Start Versioned API Example 2
-         :end-before: End Versioned API Example 2
+         :start-after: Start Stable API Example 2
+         :end-before: End Stable API Example 2
 
    .. tab::
       :tabid: nodejs
@@ -432,8 +432,8 @@ To create a *non-strict* client, use the following sample code:
       .. literalinclude:: /driver-examples/VersionedApiExamples.cs
          :language: csharp
          :dedent: 12
-         :start-after: Start Versioned API Example 3
-         :end-before: End Versioned API Example 3
+         :start-after: Start Stable API Example 3
+         :end-before: End Stable API Example 3
 
    .. tab::
       :tabid: nodejs