Sync testing php-sdk (#83)

follow-up for line/line-bot-sdk-php#640

if
https://github.com/line/line-openapi/actions/runs/13196651796/job/36839359544?pr=83#step:12:1
shows no diff, it's expected.

Author: Yang-33

.github/workflows/sdk-testing.yml

@@ -131,7 +131,7 @@ jobs:
           php-version: '8.2'
 
       - name: Install openapi-generator-cli
-        run: echo "OPENAPI_GENERATOR_VERSION=6.6.0" >> $GITHUB_ENV
+        run: echo "OPENAPI_GENERATOR_VERSION=7.10.0" >> $GITHUB_ENV
       - uses: actions/cache@v3
         id: openapi-generator-cache
         env: