We no longer need these.

Didn't make sense to have the `replacePdfFieldFont` function do things
related to command line argument parsing.

I had done it that way originally because that's how my mind worked out
the standard input and output handling at the time.

I'm not using tests here, so rather than keep useless tests cluttering
the project I decided to remove them.

This causes the `mvn package` task to fail, so I added a skip test
configuration on the Maven Surefire plugin as described by smp7d
(https://stackoverflow.com/users/395975/smp7d) on Stack Overflow:
https://stackoverflow.com/questions/7456006/maven-package-install-without-test-skip-tests/7502723#7502723

I had used Java 11 in order to use the `var` syntax, which seemed
pleasantly more concise, however, I discovered that the machine I want
to deploy this application to only has a Java 8 SDK, and I don't want to
bother messing with it and going on a potential yak shaving quest.

Make the program dynamic and use the command line arguments when
performing font replacement.

Set `input`, `find`, `replace`, and `output` from command line
arguments. These will be used to generate the output PDF.

Thanks to this Stack Overflow answer by mysomic
(https://stackoverflow.com/users/27241/mysomic) for explaining how to
get the program version in a Maven pom.xml context:
https://stackoverflow.com/questions/2712970/get-maven-artifact-version-at-runtime/12571330#12571330