.github/workflows/ci-sage.yml: Test with Singular/FLINT upgrade at sagemath/sage#37203

Author: mkoeppe

.github/workflows/ci-sage.yml

@@ -86,8 +86,8 @@ jobs:
       # Sage distribution packages to build
       targets: SAGE_CHECK=no SAGE_CHECK_flint=yes flint
       # Standard setting: Test the current beta release of Sage:
-      sage_repo: sagemath/sage
-      sage_ref: develop
+      sage_repo: mkoeppe/sage
+      sage_ref: gmp_require_6_2_1
       upstream_artifact: upstream
       # Docker targets (stages) to tag
       docker_targets: "with-targets"
@@ -104,17 +104,17 @@ jobs:
          ["latest", "",           "homebrew-macos-usrlocal-standard"]]
       targets: SAGE_CHECK=no SAGE_CHECK_flint=yes flint
       # Standard setting: Test the current beta release of Sage:
-      sage_repo:         sagemath/sage
-      sage_ref:          develop
+      sage_repo: mkoeppe/sage
+      sage_ref: gmp_require_6_2_1
       upstream_artifact: upstream
     needs: [dist]
 
   sage:
     uses: sagemath/sage/.github/workflows/docker.yml@develop
     with:
       # Standard setting: Test the current beta release of Sage:
-      sage_repo: sagemath/sage
-      sage_ref: develop
+      sage_repo: mkoeppe/sage
+      sage_ref: gmp_require_6_2_1
       upstream_artifact: upstream
       # Build incrementally from published Docker image
       incremental: true