Fix gitignore paths for debugger-frontend (#54756)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/54756

Move blanket `packages/**/dist/` rule added in D77591742 into scoped `.gitignore` for `debugger-shell`.

This was preventing new files added to `packages/debugger-frontend/dist/` from being staged.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D88172611

fbshipit-source-id: 428fffd46f5f76ddf422a41b57e7b47446c40e43

.gitignore

@@ -176,6 +176,3 @@ fix_*.patch
 
 # [Experimental] Generated TS type definitions
 /packages/**/types_generated/
-
-/packages/debugger-shell/build/
-/packages/*/dist/

packages/debugger-shell/.gitignore

@@ -0,0 +1,6 @@
+# Dependencies
+/node_modules
+
+# Build output
+/build
+/dist