Upgrade antlr4-maven-plugin to 4.7.1

[fabriciofx]

When run ANTLRv4 to generate sources, if we are using the latest version (4.7) it will show to us a warning message: ANTLR Tool version 4.5.3 used for code generation does not match the current runtime version 4.7ANTLR Tool version 4.5.3 used for code generation does not match the current runtime version 4.7.
To fix it, we need upgrade antlr4-maven-plugin plugin to version 4.7.1.

[0crat]

@yegor256/z please, pay attention to this issue

[0crat]

@fabriciofx/z this project will fix the problem faster if you donate a few dollars to it; just click here and pay via Stripe, it's very fast, convenient and appreciated; thanks a lot!

[yegor256]

@fabriciofx done in 3e89cca

[0crat]

Job gh:jcabi/jcabi-parent#84 is not assigned, can't get performer

[0crat]

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