fix: update yamlfix to 1.19.1 and fail CI on yaml lint differences

- Bump yamlfix from 1.17.0 to 1.19.1
- Add --exit-code to git diff in yamlfix step so CI fails when
  yamlfix flags formatting differences

Signed-off-by: saumya <saumyakr2006@gmail.com>

Author: oksaumya

.github/workflows/github-actions-yaml-test.yml

@@ -23,7 +23,7 @@ jobs:
     - name: Install dependencies
       run: |
         python3 -m venv venv
-        venv/bin/pip install --quiet pyyaml yamlfix==1.17.0
+        venv/bin/pip install --quiet pyyaml yamlfix==1.19.1
     - name: Run generate-variables-docs.py
       run: |
         venv/bin/python3 flow/scripts/generate-variables-docs.py
@@ -40,4 +40,4 @@ jobs:
         yamlfix --version
         set -x
         yamlfix -c yamlfix.toml flow/scripts/variables.yaml
-        git diff flow/scripts/variables.yaml
+        git diff --exit-code flow/scripts/variables.yaml