.Net: Fixed typos (#9503)

### Motivation and Context

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Fixed typos that are blocking other PRs from merge due to Spell Checker.

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

.github/_typos.toml

@@ -23,6 +23,7 @@ extend-exclude = [
     "PopulationByCountry.csv",
     "PopulationByAdmin1.csv",
     "WomensSuffrage.txt",
+    "SK-dotnet.sln.DotSettings"
 ]
 
 [default.extend-words]

dotnet/src/Agents/UnitTests/Core/History/MockHistoryGenerator.cs

@@ -30,7 +30,7 @@ public static IEnumerable<ChatMessageContent> CreateHistoryWithUserInput(int mes
         {
             yield return
                 index % 2 == 1 ?
-                    new ChatMessageContent(AuthorRole.Assistant, $"asistant response: {index}") :
+                    new ChatMessageContent(AuthorRole.Assistant, $"assistant response: {index}") :
                     new ChatMessageContent(AuthorRole.User, $"user input: {index}");
         }
     }
@@ -49,18 +49,18 @@ public static IEnumerable<ChatMessageContent> CreateHistoryWithUserInput(int mes
     public static IEnumerable<ChatMessageContent> CreateHistoryWithFunctionContent()
     {
         yield return new ChatMessageContent(AuthorRole.User, "user input: 0");
-        yield return new ChatMessageContent(AuthorRole.Assistant, "asistant response: 1");
+        yield return new ChatMessageContent(AuthorRole.Assistant, "assistant response: 1");
         yield return new ChatMessageContent(AuthorRole.User, "user input: 2");
-        yield return new ChatMessageContent(AuthorRole.Assistant, "asistant response: 3");
+        yield return new ChatMessageContent(AuthorRole.Assistant, "assistant response: 3");
         yield return new ChatMessageContent(AuthorRole.User, "user input: 4");
         yield return new ChatMessageContent(AuthorRole.Assistant, [new FunctionCallContent("function call: 5")]);
         yield return new ChatMessageContent(AuthorRole.Tool, [new FunctionResultContent("function result: 6")]);
-        yield return new ChatMessageContent(AuthorRole.Assistant, "asistant response: 7");
+        yield return new ChatMessageContent(AuthorRole.Assistant, "assistant response: 7");
         yield return new ChatMessageContent(AuthorRole.User, "user input: 8");
         yield return new ChatMessageContent(AuthorRole.Assistant, [new FunctionCallContent("function call: 9")]);
         yield return new ChatMessageContent(AuthorRole.Tool, [new FunctionResultContent("function result: 10")]);
-        yield return new ChatMessageContent(AuthorRole.Assistant, "asistant response: 11");
+        yield return new ChatMessageContent(AuthorRole.Assistant, "assistant response: 11");
         yield return new ChatMessageContent(AuthorRole.User, "user input: 12");
-        yield return new ChatMessageContent(AuthorRole.Assistant, "asistant response: 13");
+        yield return new ChatMessageContent(AuthorRole.Assistant, "assistant response: 13");
     }
 }