.Net: Fix the unknow typo (microsoft#11260)

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- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
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Author: markwallace-microsoft

dotnet/src/Extensions/Extensions.UnitTests/PromptTemplates/Handlebars/HandlebarsPromptTemplateFactoryTests.cs

@@ -27,7 +27,7 @@ public void ItCreatesHandlebarsPromptTemplate()
     }
 
     [Fact]
-    public void ItThrowsExceptionForUnknowPromptTemplateFormat()
+    public void ItThrowsExceptionForUnknownPromptTemplateFormat()
     {
         // Arrange
         var templateString = "{{input}}";

dotnet/src/SemanticKernel.UnitTests/PromptTemplate/AggregatorPromptTemplateFactoryTests.cs

@@ -33,7 +33,7 @@ public void ItCreatesMyPromptTemplates()
     }
 
     [Fact]
-    public void ItThrowsExceptionForUnknowPromptTemplateFormat()
+    public void ItThrowsExceptionForUnknownPromptTemplateFormat()
     {
         // Arrange
         var templateString = "{{$input}}";

dotnet/src/SemanticKernel.UnitTests/PromptTemplate/KernelPromptTemplateFactoryTests.cs

@@ -38,7 +38,7 @@ public void ItCreatesBasicPromptTemplate()
     }
 
     [Fact]
-    public void ItThrowsExceptionForUnknowPromptTemplateFormat()
+    public void ItThrowsExceptionForUnknownPromptTemplateFormat()
     {
         // Arrange
         var templateString = "{{$input}}";

dotnet/src/SemanticKernel.UnitTests/Utilities/AIConnectors/FunctionCallsProcessorTests.cs

@@ -768,7 +768,7 @@ await this._sut.ProcessFunctionCallsAsync(
     }
 
     [Fact]
-    public async Task ItShouldSerializeFunctionResultOfUnknowTypeAsync()
+    public async Task ItShouldSerializeFunctionResultOfUnknownTypeAsync()
     {
         // Arrange
         var function1 = KernelFunctionFactory.CreateFromMethod(() => { return new { a = 2, b = "test" }; }, "Function1");