tag doc: move the description of --[no-]merged earlier

Move the documentation for the --merged & --no-merged options earlier
in the documentation, to sit along the other switches, and right next
to the similar --contains and --points-at switches.

It makes more sense to group the options together, not have some
options after the like of <tagname>, <object>, <format> etc.

This was originally put there when the --merged & --no-merged options
were introduced in 5242860 ("tag.c: implement '--merged' and
'--no-merged' options", 2015-09-10). It's not apparent from that
commit that the documentation is being placed apart from other
options, rather than along with them, so this was likely missed in the
initial review.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-tag.txt

@@ -124,6 +124,11 @@ This option is only applicable when listing tags without annotation lines.
 	Only list tags which contain the specified commit (HEAD if not
 	specified).
 
+--[no-]merged [<commit>]::
+	Only list tags whose tips are reachable, or not reachable
+	if `--no-merged` is used, from the specified commit (`HEAD`
+	if not specified).
+
 --points-at <object>::
 	Only list tags of the given object.
 
@@ -173,11 +178,6 @@ This option is only applicable when listing tags without annotation lines.
 	that of linkgit:git-for-each-ref[1].  When unspecified,
 	defaults to `%(refname:strip=2)`.
 
---[no-]merged [<commit>]::
-	Only list tags whose tips are reachable, or not reachable
-	if `--no-merged` is used, from the specified commit (`HEAD`
-	if not specified).
-
 CONFIGURATION
 -------------
 By default, 'git tag' in sign-with-default mode (-s) will use your