[XrossFox]

Description

• Set ContentType.RESOURCE in BatchGetAssetsHistoryExample
• Create and clean up a temporary GCS bucket in QuickStartIT for testBatchGetAssetsHistory

Fixes b/575851644

Checklist

Testing

• I have tested this change on a live environment and verified it works as intended.
• Tests pass: mvn clean verify required
• Lint passes: mvn -P lint checkstyle:check required
• Static Analysis: mvn -P lint clean compile pmd:cpd-check spotbugs:check advisory only

Compliance & Style

• I have followed Sample Format Guide
• pom.xml parent set to latest shared-configuration
• Appropriate changes to README are included in PR
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample

Post-Approval Actions

• Please merge this PR for me once it is approved

[gemini-code-assist]

Code Review

This pull request updates BatchGetAssetsHistoryExample.java to use ContentType.RESOURCE instead of ContentType.CONTENT_TYPE_UNSPECIFIED. It also refactors QuickStartIT.java to use a dynamically created and deleted temporary bucket for the BatchGetAssetsHistory test. Feedback was provided on QuickStartIT.java to remove a redundant !got.isEmpty() check, as the output stream will always contain at least a newline character, making the conditional check unnecessary.

[amcolin]

Great fix!
Since we're making these changes, here are two small things we can clean up/remove