CI: remove pxf_fdw from CI workflow

Similar to PR #1549, we will keep the pxf_fdw in `apache/cloudberry-pxf`
as the latest version, so remove pxf_fdw test from this CI workflow
file.

Author: tuhaihe

.github/workflows/build-cloudberry-rocky8.yml

@@ -316,7 +316,6 @@ jobs:
               },
               {"test":"ic-gpcontrib",
                "make_configs":["gpcontrib/orafce:installcheck",
-                               "gpcontrib/pxf_fdw:installcheck",
                                "gpcontrib/zstd:installcheck",
                                "gpcontrib/gp_sparse_vector:installcheck",
                                "gpcontrib/gp_toolkit:installcheck"]