mke2fs: accept the english yes character to the proceed question

mke2fs: accept the english yes character to the proceed question

In some cases if the translation file is missing some translations,
mke2fs can end up printing an English message, e.g.:

% LANG=it_IT.UTF-8 ./mke2fs /tmp/foo.img 8M
mke2fs 1.45.1 (12-May-2019)
/tmp/foo.img contiene un file system ext4
	created on Mon May 27 19:35:48 2019
Proceed anyway? (y,N)

However, if there is a translation for string to match with "yY"
(e.g., to "sS" for Italian), then 'y' won't work.  Fix this by falling
back to the english 'yY' characters.

Addresses-Debian-Bug: #907034
Signed-off-by: Theodore Ts'o <tytso@mit.edu>