l10n: de.po: consistent translation of 'root commit'

'root commit' is usually translated as 'Root-Commit'. But in one
occasion it‘s translated as 'Basis-Commit' which is the translation
for 'base commit'.

Signed-off-by: Sebastian Staudt <koraktor@gmail.com>

po/de.po

@@ -4870,7 +4870,7 @@ msgstr "losgelöster HEAD"
 #: sequencer.c:1256
 msgid " (root-commit)"
-msgstr " (Basis-Commit)"
+msgstr " (Root-Commit)"
 #: sequencer.c:1277
 msgid "could not parse HEAD"