chore: exclude tarball from code generation

        autosynth cannot find the source of changes triggered by earlier changes in this
        repository, or by version upgrades to tools such as linters.

-amend

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/python-bigquery.git",
-        "sha": "1c6681aba872c00afb16a904a2ba9bae8e9618d3"
+        "sha": "1823cadee3acf95c516d0479400e4175349ea199"
       }
     },
     {
@@ -93,7 +93,6 @@
     "CONTRIBUTING.rst",
     "LICENSE",
     "MANIFEST.in",
-    "bigquery-v2-py.tar.gz",
     "docs/_static/custom.css",
     "docs/_templates/layout.html",
     "docs/bigquery_v2/model_service.rst",

synth.py

@@ -32,6 +32,7 @@
 s.move(
     library,
     excludes=[
+        "*.tar.gz",
         "docs/index.rst",
         "docs/bigquery_v2/*_service.rst",
         "docs/bigquery_v2/services.rst",