Revert "chore: pin versions of dependencies for compatibility with Py… (#781)

…thon 3.6 (#1588) (#756)"

This reverts commit 32474d0.

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:
- [ ] Make sure to open an issue as a [bug/issue](https://togithub.com/googleapis/java-bigqueryconnection/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
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Fixes #<issue_number_goes_here> ☕️

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Author: diegomarquezp

java-bigqueryconnection/.github/.OwlBot.lock.yaml

@@ -13,5 +13,4 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-java:latest
-  digest: sha256:6566dc8226f20993af18e5a4e7a2b1ba85a292b02dedb6a1634cf10e1b418fa5
-
+  digest: sha256:f14e3fefe8e361e85752bd9890c8e56f2fe25f1e89cbb9597e4e3c7a429203a3

java-bigqueryconnection/renovate.json

@@ -10,6 +10,7 @@
     ":maintainLockFilesDisabled",
     ":autodetectPinVersions"
   ],
+  "ignorePaths": [".kokoro/requirements.txt"],
   "packageRules": [
     {
       "packagePatterns": [