deps: update core dependencies to v29 (major) (#114)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| com.google.guava:guava | major | `28.2-android` -> `29.0-android` |
| [com.google.guava:guava-bom](https://togithub.com/google/guava) | major | `28.2-android` -> `29.0-android` |

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pom.xml

@@ -63,7 +63,7 @@
     <google.core.version>1.93.4</google.core.version>
     <gax.version>1.56.0</gax.version>
     <http-client-bom.version>1.34.2</http-client-bom.version>
-    <guava.version>28.2-android</guava.version>
+    <guava.version>29.0-android</guava.version>
     <junit.version>4.13</junit.version>
     <google.common-protos.version>1.18.0</google.common-protos.version>
     <protobuf.version>3.11.4</protobuf.version>