.Net: Update README.md (#12790)

### Changed WebPlaugins to WebPlugins

### Motivation and Context

1. **Why is this change required?**  
Corrects a minor typo in the README or comments where "WebPlaugins" was
mistakenly written instead of "WebPlugins".

2. **What problem does it solve?**  
Fixes a spelling mistake that could confuse users or make the
documentation/search indexing inaccurate.

3. **What scenario does it contribute to?**  
Improves readability and professionalism of the documentation by
correcting the plugin name.

4. **If it fixes an open issue, please link to the issue here.**  
   _N/A_ — No associated issue, minor documentation fix.

---

### Description

Corrected the spelling of “WebPlaugins” to “WebPlugins” in the relevant
Markdown link and text. No changes were made to the underlying code or
logic. This improves clarity and ensures consistency in plugin naming.

---

### Contribution Checklist

- [x] The code builds clean without any errors or warnings (N/A for
doc-only change)
- [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
- [ ] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

Co-authored-by: SergeyMenshykh <68852919+SergeyMenshykh@users.noreply.github.com>

Author: brijesh-9665

dotnet/samples/Concepts/README.md

@@ -187,7 +187,7 @@ dotnet test -l "console;verbosity=detailed" --filter "FullyQualifiedName=ChatCom
 - [ImportPluginFromGrpc](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/Plugins/ImportPluginFromGrpc.cs)
 - [TransformPlugin](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/Plugins/TransformPlugin.cs)
 - [CopilotAgentBasedPlugins](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/Plugins/CopilotAgentBasedPlugins.cs)
-- [WebPlaugins](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/Plugins/WebPlugins.cs)
+- [WebPlugins](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/samples/Concepts/Plugins/WebPlugins.cs)
 
 ### PromptTemplates - Using [`Templates`](https://github.com/microsoft/semantic-kernel/blob/main/dotnet/src/SemanticKernel.Abstractions/PromptTemplate/IPromptTemplate.cs) with parametrization for `Prompt` rendering