fix: paper server jar input rule (#3494)
fix: paper server jar input rule (#3494)

Changes Paper egg server jar variable input rule to match the other Minecraft eggs. Matches `a-zA-Z0-9_` and `.jar` at the end instead of hard-coded length value of 20.

Fixes #3492
Pterodactyl/Panel,Pterodactyl/Panel,Pterodactyl/Panel,Pterodactyl/Panel