Use correct SOABI for coverage wheels on macOS x86-64/Python 3.14 (#276)

Looks like PyPI is now building x86-64 binary wheels for Python 3.14 against
macOS 10.15+ instead of 10.13+ - fix the download URLs for the coverage
module.

Author: chrisnovakovic

third_party/python/BUILD

@@ -109,6 +109,8 @@ _coverage_tags = {
             ["cp312", "cp312"],
             ["cp313", "cp313"],
             ["cp313", "cp313t"],
+        ],
+        "macosx_10_15_x86_64": [
             ["cp314", "cp314"],
             ["cp314", "cp314t"],
         ],