Remove Guava dependency

[tinacious]

Closes https://github.com/outfoxx/typescriptpoet/issues/28

As described in the issue, this library has several CVEs that have been resolved in later versions and doesn't appear to be used in the project (likely was added in the initial bootstrapping by IntelliJ).

This commit removes it and the "Miscellaneous" section in the Gradle file since that was the only item there.

All tests still appear to pass locally.

This looks like a related PR that tried to solve this a while back: https://github.com/outfoxx/typescriptpoet/pull/20