Tweak dependencies to suppress aggressive Guava warning

Guava 30.1.1-android adds an obtrusive warning regarding the intent to remove support for Java 7 in an unspecified future release. I figured out a way to suppress the warning, but this requires pulling in guava transitively through guava-agent:

com.nordstrom.tools:guava-agent:30.1.1a
└── com.google.guava:guava:30.1.1-android