fix: update default sample row key attempt timeout to 5 min (#1827)

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-bigtable/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
- [ ] Ensure the tests and linter pass
- [ ] Code coverage does not decrease (if any source code was changed)
- [ ] Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> ☕️

If you write sample code, please follow the [samples format](
https://togithub.com/GoogleCloudPlatform/java-docs-samples/blob/main/SAMPLE_FORMAT.md).

Author: mutianf

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/EnhancedBigtableStubSettings.java

@@ -387,8 +387,8 @@ public ServerStreamingCallSettings<Query, Row> readRowsSettings() {
    *       starts} at 10ms and {@link RetrySettings.Builder#setRetryDelayMultiplier increases
    *       exponentially} by a factor of 2 until a {@link RetrySettings.Builder#setMaxRetryDelay
    *       maximum of} 1 minute.
-   *   <li>The default timeout for {@link RetrySettings.Builder#setMaxRpcTimeout each attempt} is 20
-   *       seconds and the timeout for the {@link RetrySettings.Builder#setTotalTimeout entire
+   *   <li>The default timeout for {@link RetrySettings.Builder#setMaxRpcTimeout each attempt} is 5
+   *       minutes and the timeout for the {@link RetrySettings.Builder#setTotalTimeout entire
    *       operation} across all of the attempts is 10 mins.
    * </ul>
    */
@@ -659,7 +659,12 @@ private Builder() {
       sampleRowKeysSettings = UnaryCallSettings.newUnaryCallSettingsBuilder();
       sampleRowKeysSettings
           .setRetryableCodes(IDEMPOTENT_RETRY_CODES)
-          .setRetrySettings(IDEMPOTENT_RETRY_SETTINGS);
+          .setRetrySettings(
+              IDEMPOTENT_RETRY_SETTINGS
+                  .toBuilder()
+                  .setInitialRpcTimeout(Duration.ofMinutes(5))
+                  .setMaxRpcTimeout(Duration.ofMinutes(5))
+                  .build());
 
       mutateRowSettings = UnaryCallSettings.newUnaryCallSettingsBuilder();
       copyRetrySettings(baseDefaults.mutateRowSettings(), mutateRowSettings);