glibc: Fix brew audit glibc for Linuxbrew
glibc: Fix brew audit glibc for Linuxbrew

Fix the error:
Please use "https://ftp.gnu.org/gnu/glibc/glibc-2.19.tar.bz2"
instead of https://ftpmirror.gnu.org/glibc/glibc-2.19.tar.bz2.

LinuxbrewTestBot/homebrew-core,Linuxbrew/homebrew-core,maxim-belkin/homebrew-core,LinuxbrewTestBot/homebrew-core,Linuxbrew/homebrew-core,maxim-belkin/homebrew-core,rwhogg/homebrew-core,rwhogg/homebrew-core