Fix instruction for local development branch (#1305)

## Summary
Just a simple one-word doc change

## Additional background
I tried to follow instructions in `CONTRIBUTING.md` and found that the `git pull` command as documented before this change resulted in an error message.

## Checklist

The proposed changes:
- [x] fix a bug in AMReX documentation


Co-authored-by: Klaus Weide <>

CONTRIBUTING.md

@@ -82,7 +82,7 @@ Now you are free to play with your fork (for additional information, you can vis
 > on your fork with
 > ```
 > git checkout development
-> git pull development
+> git pull
 > ```
 
 Make sure you are on the `development` branch with