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>