Fixed the baseline tests to account for the solution file extension change

Author: mkArtakMSFT

Diff for: src/ProjectTemplates/test/Templates.Tests/BaselineTest.cs

@@ -91,7 +91,7 @@ public async Task Template_Produces_The_Right_Set_Of_FilesAsync(string arguments
             if (relativePath.EndsWith(".csproj", StringComparison.Ordinal) ||
                 relativePath.EndsWith(".fsproj", StringComparison.Ordinal) ||
                 relativePath.EndsWith(".props", StringComparison.Ordinal) ||
-                relativePath.EndsWith(".sln", StringComparison.Ordinal) ||
+                relativePath.EndsWith(".slnx", StringComparison.Ordinal) ||
                 relativePath.EndsWith(".targets", StringComparison.Ordinal) ||
                 relativePath.StartsWith("bin/", StringComparison.Ordinal) ||
                 relativePath.StartsWith("obj/", StringComparison.Ordinal) ||