libext2fs: fix a minor grammatical error in the error catalog

'an block' should be 'a block'.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/po/de.po b/po/de.po
index 0e7b39e..b7f71c2 100644
--- a/po/de.po
+++ b/po/de.po
@@ -5976,7 +5976,7 @@
 msgstr "Die Inode-Bitmap kann nicht gelesen werden"
 
 #: lib/ext2fs/ext2_err.c:40
-msgid "Can't write an block bitmap"
+msgid "Can't write a block bitmap"
 msgstr "Die Block-Bitmap kann nicht geschrieben werden"
 
 #: lib/ext2fs/ext2_err.c:41