chore: update kokoro config (via synth) (#556)

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Synth log will be available here:
https://source.cloud.google.com/results/invocations/abd11f9f-00ea-4883-9679-79e339a91948/targets

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Source-Link: https://github.com/googleapis/synthtool/commit/ffe10407ee2f261c799fb0d01bf32a8abc67ed1e
diff --git a/synth.metadata b/synth.metadata
index 0efbe1e..901a2cb 100644
--- a/synth.metadata
+++ b/synth.metadata
@@ -3,15 +3,15 @@
     {
       "git": {
         "name": ".",
-        "remote": "git@github.com:googleapis/google-auth-library-python",
-        "sha": "aab4f2fdb2cfa598397026865ccb270a05c38cc4"
+        "remote": "https://github.com/googleapis/google-auth-library-python.git",
+        "sha": "218a159f646c81021c890b92f9cff003aed949a8"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "71b8a272549c06b5768d00fa48d3ae990e871bec"
+        "sha": "ffe10407ee2f261c799fb0d01bf32a8abc67ed1e"
       }
     }
   ]