Update Barrel.java - Githubissues

Short Description

Changed the Barrel 'Extract all' button's display item to red stained glass panes, to better contrast with the orange stained glass pane GUI border.

See above.

No open issues.

[X] I have fully tested the proposed changes and promise that they will not break everything into chaos.
[X] I have tested every variant of every item or config setting that I have added.
[X] I have also tested the proposed changes in combination with base Slimefun and made sure nothing breaks/unexpected happens.
[X] I followed the existing code standards and didn't mess up the formatting.
[] I did my best to add documentation to any public classes or methods I added which may not be obvious to maintainers.
[] I have added Nonnull and Nullable annotations to my methods to indicate their behaviour for null values