Fix typo in Gentoo docstring (#6303)

util/linux_install.sh

@@ -2,7 +2,7 @@
 
 # Note: This file uses tabs to indent. Please don't mix tabs and spaces.
 
-GENTOO_WARNING="This script will make a USE change in order to ensure that that QMK works on your system. All changes will be sent to the the file /etc/portage/package.use/qmk_firmware -- please review it, and read Portage's output carefully before installing any packages on your system. You will also need to ensure that your kernel is compiled with support for the keyboard chip that you are using (e.g. enable Arduino for the Pro Micro). Further information can be found on the Gentoo wiki."
+GENTOO_WARNING="This script will make a USE change in order to ensure that that QMK works on your system. All changes will be sent to the the file /etc/portage/package.use/qmkfirmware -- please review it, and read Portage's output carefully before installing any packages on your system. You will also need to ensure that your kernel is compiled with support for the keyboard chip that you are using (e.g. enable Arduino for the Pro Micro). Further information can be found on the Gentoo wiki."
 
 SLACKWARE_WARNING="You will need the following packages from slackbuilds.org:\n\tarm-binutils\n\tarm-gcc\n\tavr-binutils\n\tavr-gcc\n\tavr-libc\n\tavrdude\n\tdfu-programmer\n\tdfu-util\n\tnewlib\nThese packages will be installed with sudo and sboinstall, so ensure that your user is added to sudoers and that sboinstall is configured."