tests: remove "cat foo" before "test_i18ngrep bar foo"

tests: remove "cat foo" before "test_i18ngrep bar foo"

Some tests print a file before searching for a pattern using
test_i18ngrep.  This is useful when debugging tests with --verbose when
the pattern is not found as expected.

Since 63b1a175ee (t: make 'test_i18ngrep' more informative on failure,
2018-02-08) test_i18ngrep already shows the contents of a file that
doesn't match the expected pattern, though.

So don't bother doing the same unconditionally up-front.  The contents
are not interesting if the expected pattern is found, and showing it
twice if it doesn't match is of no use.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>