audio/lash: Fixed.pc file: removed Requires line, added missing USE statements

• Removed Requires in .pc because it causes pkg-config to pass jack libraries to users that users don't need
• Add needed USE_GNOME=gdkpixbuf2 cairo
• PYTHON_CONFIGURE_ENABLE=pylash - pylash is still broken as before.

PR: 220956
Submitted by: Yuri Victorovich <yuri@rawbw.com>