docs: typo in greeting template (#2936)

Typo

The comma after "contribution" isn't necessary, and "great first issue!" works fine as a separate exclamation.

(cherry picked from commit 3a9bb52)

Author: MostHumble

.github/workflows/greetings.yml

@@ -10,5 +10,5 @@ jobs:
       - uses: actions/first-interaction@v1
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
-          issue-message: "Hi! thanks for your contribution!, great first issue!"
+          issue-message: "Hi! Thanks for your contribution! Great first issue!"
           pr-message: "Hey thanks for the input! Please give us a bit of time to review it!"