MINOR: [Go] [Benchmarking] fix repo specifier (#36104)

The Arrow Conbench deployment recently imposed stricter validation, that the `repository` key must be a URL.

This PR fixes the Go benchmarking script to comply.

Authored-by: Austin Dickey <austin3spammy@gmail.com>
Signed-off-by: Matt Topol <zotthewizard@gmail.com>

ci/scripts/go_bench_adapt.py

@@ -41,7 +41,7 @@
     # Assume GitHub Actions CI. The environment variable lookups below are
     # expected to fail when not running in GitHub Actions.
     github_commit_info = {
-        "repository": os.environ["GITHUB_REPOSITORY"],
+        "repository": f'{os.environ["GITHUB_SERVER_URL"]}/{os.environ["GITHUB_REPOSITORY"]}',
         "commit": os.environ["GITHUB_SHA"],
         "pr_number": None,  # implying default branch
     }