[GitHub][workflows] Run automation script with python3 (llvm#78695)

This means we don't have to chmod, or change permissions any other way.

Author: DavidSpickett

.github/workflows/issue-subscriber.yml

@@ -22,7 +22,6 @@ jobs:
       - name: Setup Automation Script
         working-directory: ./llvm/utils/git/
         run: |
-          chmod a+x github-automation.py
           pip install -r requirements.txt
 
       - name: Update watchers
@@ -31,7 +30,7 @@ jobs:
         env:
           LABEL_NAME: ${{ github.event.label.name }}
         run: |
-          ./github-automation.py \
+          python3 ./github-automation.py \
             --token '${{ secrets.ISSUE_SUBSCRIBER_TOKEN }}' \
             issue-subscriber \
             --issue-number '${{ github.event.issue.number }}' \

.github/workflows/new-prs.yml

@@ -43,13 +43,12 @@ jobs:
       - name: Setup Automation Script
         working-directory: ./llvm/utils/git/
         run: |
-          chmod a+x github-automation.py
           pip install -r requirements.txt
 
       - name: Greet Author
         working-directory: ./llvm/utils/git/
         run: |
-          ./github-automation.py \
+          python3 ./github-automation.py \
             --token '${{ secrets.GITHUB_TOKEN }}' \
             pr-greeter \
             --issue-number "${{ github.event.pull_request.number }}"

.github/workflows/pr-subscriber.yml

@@ -22,13 +22,12 @@ jobs:
       - name: Setup Automation Script
         working-directory: ./llvm/utils/git/
         run: |
-          chmod a+x github-automation.py
           pip install -r requirements.txt
 
       - name: Update watchers
         working-directory: ./llvm/utils/git/
         run: |
-          ./github-automation.py \
+          python3 ./github-automation.py \
             --token '${{ secrets.ISSUE_SUBSCRIBER_TOKEN }}' \
             pr-subscriber \
             --issue-number "${{ github.event.number }}" \