repart: Fix misleading typo in GPT partition flag

Bit 60 is the one corresponding to ReadOnly, not 50.  Fix this.

(cherry picked from commit 932cc94436e653d0487c29e0dd44685610cd7bcb)
(cherry picked from commit 2665618555d08fc3877043cac392f1b6573811b7)
(cherry picked from commit f38c19b)
(cherry picked from commit 5ae6c77)

man/repart.d.xml

@@ -587,7 +587,7 @@
         <citerefentry
         project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 
-        <para>If both bit 50 and 59 are set for a partition (i.e. the partition is marked both read-only and
+        <para>If both bit 60 and 59 are set for a partition (i.e. the partition is marked both read-only and
         marked for file system growing) the latter is typically without effect: the read-only flag takes
         precedence in most tools reading these flags, and since growing the file system involves writing to
         the partition it is consequently ignored.</para>