minor #17020 [ci] allow flex to run in CI (jrushlow)

This PR was merged into the 4.4 branch.

Discussion
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[ci] allow flex to run in CI

Since Composer 2.3.9 unless you explicitly allow/disallow a plugin (flex in our case), an error is thrown (halts our CI run) before any tests are actually ran. (Code Blocks)

Commits
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fb505de [ci] allow flex to run in CI

Author: javiereguiluz

.github/workflows/ci.yaml

@@ -116,6 +116,11 @@ jobs:
             if: ${{ steps.find-files.outputs.files }}
             run: composer create-project symfony-tools/code-block-checker:@dev _checker
 
+          - name: Allow Flex
+            if: ${{ steps.find-files.outputs.files }}
+            run: |
+              composer config --no-plugins allow-plugins.symfony/flex true
+
           - name: Install test application
             if: ${{ steps.find-files.outputs.files }}
             run: |