cgitrc.5.txt: fix description and markup for 'snapshots' option

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgitrc.5.txt

@@ -217,14 +217,9 @@ root-title::
 	"Git Repository Browser".
 
 snapshots::
-	Text which specifies the default (and allowed) set of snapshot formats
-	supported by cgit. The value is a space-separated list of zero or more
-	of the following values:
-		"tar"		uncompressed tar-file
-		"tar.gz"	gzip-compressed tar-file
-		"tar.bz2"	bzip-compressed tar-file
-		"zip"		zip-file
-	Default value: none.
+	Text which specifies the default set of snapshot formats generated by
+	cgit. The value is a space-separated list of zero or more of the
+	values "tar", "tar.gz", "tar.bz2" and "zip". Default value: none.
 
 source-filter::
 	Specifies a command which will be invoked to format plaintext blobs