fix: remove --dev flag from uv sync and clean up .gitignore

Author: taeold

.github/CONTRIBUTING.md

@@ -32,7 +32,7 @@ curl -LsSf https://astral.sh/uv/install.sh | sh
 # Clone and setup the project
 git clone https://github.com/firebase/firebase-functions-python.git
 cd firebase-functions-python
-uv sync --dev
+uv sync
 ```
 
 This will automatically:

.gitignore

@@ -139,8 +139,3 @@ doc/dist
 .idea
 .vscode/*
 !.vscode/settings.json
-
-# Local development files
-async.md
-modernization.md
-uv.lock