gitk: Adjust two equal strings which differed in whitespace

gitk: Adjust two equal strings which differed in whitespace

There were the two strings "SHA1 ID: " and "SHA1 ID:" as description
for the SHA1 search textbox.  Change it to two equal strings, the
space is now outside of the translated string.

Furthermore the German translation wasn't unique, but "SHA1:" resp.
"SHA1-Hashwert:". The former was displayed after initialisation, the
latter after changes to the textbox, for example when clearing the text.
But it was too long to be displayed fully, so use a shorter translation.

Signed-off-by: Markus Heidelberg <markus.heidelberg@web.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>