Fix the case of the filenames in Resources.resx so that it builds on Linux

[ghost]

On Linux, Rhydon currently fails to build with errors that look like this:

/usr/lib/mono/xbuild/14.0/bin/Microsoft.Common.targets: error : Tool exited with code: 1. Output: Error: Invalid ResX input.
Position: Line 123, Column 5.
Inner exception: Could not find a part of the path "[…]/Rhydon/Rhydon/resources/pokered-us.ttf".

This fixes those errors so that Rhydon can be built on Linux and other OSes with case-sensitive filesystems.