ci: make semgrep ignore existing errors (#26516)

.github/helper/semgrep_rules/frappe_correctness.yml

@@ -98,8 +98,6 @@ rules:
   languages: [python]
   severity: WARNING
   paths:
-      exclude:
-        - test_*.py
       include:
         - "*/**/doctype/*"
 

.github/workflows/semgrep.yml

@@ -1,34 +1,20 @@
 name: Semgrep
 
 on:
-  pull_request:
-    branches:
-      - develop
-      - version-13-hotfix
-      - version-13-pre-release
+  pull_request: { }
+  push:
+      branches: ["develop"]
+
 jobs:
   semgrep:
     name: Frappe Linter
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-    - name: Setup python3
-      uses: actions/setup-python@v2
+      - uses: returntocorp/semgrep-action@v1
+        env:
+            SEMGREP_TIMEOUT: 120
         with:
-        python-version: 3.8
-
-    - name: Setup semgrep
-      run: |
-        python -m pip install -q semgrep
-        git fetch origin $GITHUB_BASE_REF:$GITHUB_BASE_REF -q
-
-    - name: Semgrep errors
-      run: |
-        files=$(git diff --name-only --diff-filter=d $GITHUB_BASE_REF)
-        [[ -d .github/helper/semgrep_rules ]] && semgrep --severity ERROR --config=.github/helper/semgrep_rules --quiet --error $files
-        semgrep --config="r/python.lang.correctness" --quiet --error $files
-
-    - name: Semgrep warnings
-      run: |
-        files=$(git diff --name-only --diff-filter=d $GITHUB_BASE_REF)
-        [[ -d .github/helper/semgrep_rules ]] && semgrep --severity WARNING --severity INFO --config=.github/helper/semgrep_rules --quiet $files
+            config: >-
+              r/python.lang.correctness
+              .github/helper/semgrep_rules