Potential fix for pull request finding 'Comparison between inconvertible types'

Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>

Author: alex-rawlings-yyc

src/__tests__/main.test.ts

@@ -25,7 +25,6 @@ interface PapiBackendTestMock {
 function isPapiBackendTestMock(m: unknown): m is PapiBackendTestMock {
   return (
     typeof m === 'object' &&
-    m !== undefined &&
     m instanceof Object &&
     '__mockRegisterWebViewProvider' in m &&
     '__mockOpenWebView' in m &&