updated CONTRIBUTING.md

- signed-off-by: trimstray <trimstray@gmail.com>

CONTRIBUTING.md

@@ -32,8 +32,6 @@ grep -qs "^$SOB" "$1" || echo "$SOB" >> "$1"
 
 When creating pull request, please heed the following:
 
-- Base your code on the latest master branch to avoid manual merges
+- Base your code on the latest **testing branch** to avoid manual merges
 - Code review may ensue in order to help shape your proposal
 - Explain the problem and your proposed solution
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-