Update dependency com.google.guava:guava to v30

[dev-mend-for-github-com[bot]]

This PR contains the following updates:

Package	Type	Update	Change
com.google.guava:guava	compile	major	29.0-jre -> 30.0-android

By merging this PR, the issue #11 will be automatically resolved and closed:

Severity	CVSS Score	CVE	Reachability
Low	3.3	CVE-2020-8908	Reachable

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