cleanup: removes unused kokoro config files (#212)

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Source-Link: googleapis/synthtool@4530cc6

synth.metadata

@@ -11,16 +11,16 @@
       "git": {
         "name": "googleapis",
         "remote": "https://github.com/googleapis/googleapis.git",
-        "sha": "df995b638ec02863323051599f1b4c41102ce211",
-        "internalRef": "317872942"
+        "sha": "96ef637adf148d54236ad83fefa30c7f75f29737",
+        "internalRef": "325052820"
       }
     },
     {
       "git": {
         "name": "googleapis",
         "remote": "https://github.com/googleapis/googleapis.git",
-        "sha": "df995b638ec02863323051599f1b4c41102ce211",
-        "internalRef": "317872942"
+        "sha": "96ef637adf148d54236ad83fefa30c7f75f29737",
+        "internalRef": "325052820"
       }
     },
     {