Remove GitHub workflow and Copilot files from solution

Removed .github/copilot-instructions.md, build.yml, and release.yml
from the /Solution Items/ folder in the solution file. These files
are no longer needed in the solution context.

Author: IeuanWalker

MinimalApiSourceGenerator.slnx

@@ -14,9 +14,6 @@
   </Folder>
   <Folder Name="/Solution Items/">
     <File Path=".editorconfig" />
-    <File Path=".github/copilot-instructions.md" />
-    <File Path=".github/workflows/build.yml" />
-    <File Path=".github/workflows/release.yml" />
     <File Path="coverlet.runsettings" />
     <File Path="README.md" />
   </Folder>