refactor(ci): use conventional-pr workflow from substra-gha-workflows (…

…#369)

## Description

Refactors `conventional_title` GHA workflow from generic workflow from
`substra-gha-workflows`

<!-- Please include a summary of your changes. -->

## How has this been tested?

<!-- Please describe the tests that you ran to verify your changes.  -->

## Checklist

- [ ] [changelog](../CHANGELOG.md) was updated with notable changes
- [ ] documentation was updated

Signed-off-by: Kaan Yagci <kaan.yagci-ext@owkin.com>

.github/workflows/conventional-pr.yml

@@ -9,11 +9,6 @@ on:
 
 jobs:
   conventional_title:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: amannn/action-semantic-pull-request@v5.4.0
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        with:
-          validateSingleCommit: true
-          validateSingleCommitMatchesPrTitle: true
+    uses: substra/substra-gha-workflows/.github/workflows/conventional-pr.yml@main
+    secrets:
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}