ci: bump actions/upload-artifact SHA to current v4 (#16)

Fixes estate-wide Hypatia Security Scan + Static Analysis Gate red. The
pinned SHA `65c79d7...` for `actions/upload-artifact@v4` no longer
resolves; current v4 = `ea165f8d`. Tracked in
`hyperpolymath/hypatia#213`.

Author: hyperpolymath

.github/workflows/hypatia-scan.yml

@@ -79,7 +79,7 @@ jobs:
           echo "- Medium: $MEDIUM" >> $GITHUB_STEP_SUMMARY
 
       - name: Upload findings artifact
-        uses: actions/upload-artifact@65c79d7f54e76e4e3c7a8f34db0f4ac8b515c478 # v4
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
         with:
           name: hypatia-findings
           path: hypatia-findings.json
@@ -180,4 +180,4 @@ jobs:
               repo: context.repo.repo,
               issue_number: context.issue.number,
               body: comment
-            });
+            });