t1300: demonstrate that CamelCased aliases regressed

t1300: demonstrate that CamelCased aliases regressed

It is totally legitimate to add CamelCased aliases, but due to the way
config keys are compared, the case does not matter.

Except that now it does: the alias name is expected to be all
lower-case. This is a regression introduced by a9bcf6586d1 (alias: use
the early config machinery to expand aliases, 2017-06-14).

Noticed by Alejandro Pauly, diagnosed by Kevin Willford.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>