[DOC] Fix "military timezone"

Not only `J` is called military timezone.

Author: nobu

doc/time/in.rdoc

@@ -1,7 +1,7 @@
 - <tt>in: zone</tt>: a timezone _zone_, which may be:
   - A string offset from UTC.
   - A single letter offset from UTC, in the range <tt>'A'..'Z'</tt>,
-    <tt>'J'</tt> (the so-called military timezone) excluded.
+    <tt>'J'</tt> excluded (the so-called military timezone).
   - An integer number of seconds.
   - A timezone object;
     see {Timezone Argument}[#class-Time-label-Timezone+Argument] for details.

doc/time/zone_and_in.rdoc

@@ -1,7 +1,7 @@
 - +zone+: a timezone, which may be:
   - A string offset from UTC.
   - A single letter offset from UTC, in the range <tt>'A'..'Z'</tt>,
-    <tt>'J'</tt> (the so-called military timezone) excluded.
+    <tt>'J'</tt> excluded (the so-called military timezone).
   - An integer number of seconds.
   - A timezone object;
     see {Timezone Argument}[#class-Time-label-Timezone+Argument] for details.