[ci] fetch full history for php docs

we need the full history if we want to peek at historic versions of the docs

.github/workflows/continuous-integration.yml

@@ -33,12 +33,14 @@ jobs:
         with:
           path: "generator/doc/doc-en/doc-base"
           repository: "salathe/phpdoc-base"
+          fetch-depth: 0
       - name: "Check out php/doc-en"
         uses: "actions/checkout@v4"
         if: steps.cache-php-doc.outputs.cache-hit != 'true'
         with:
           path: "generator/doc/doc-en/en"
           repository: "php/doc-en"
+          fetch-depth: 0
 
   generator_tests:
     name: "Generator Tests"