libc: remove unneeded glibc/eglibc common functions

do_libc_locales_extract() and do_libc_locales() in glibc-eglibc.sh-common have
been overridden for both glibc and eglibc, so they can now be removed, which
this patch does.

Signed-off-by: "Benoît THÉBAUDEAU" <benoit.thebaudeau@advansee.com>

 menu "Debug facilities"

 source "config.gen/debug.in"

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