doc(stash): clarify the description of save

The original phrasing of this paragraph made at least one person stumble
over the word "from" (thinking that it was a typo and "from" was
intended), and other readers chimed in, agreeing that it was confusing:
https://public-inbox.org/git/0102016b8d597569-c1f6cfdc-cb45-4428-8737-cb1bc30655d8-000000@eu-west-1.amazonses.com/#t

Let's rewrite that paragraph for clarity.

Inspired-by-a-patch-by: Catalin Criste <[email protected]>
Signed-off-by: Johannes Schindelin <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: dscho

Documentation/git-stash.txt

@@ -87,8 +87,9 @@ The `--patch` option implies `--keep-index`.  You can use
 save [-p|--patch] [-k|--[no-]keep-index] [-u|--include-untracked] [-a|--all] [-q|--quiet] [<message>]::
 
 	This option is deprecated in favour of 'git stash push'.  It
-	differs from "stash push" in that it cannot take pathspecs,
-	and any non-option arguments form the message.
+	differs from "stash push" in that it cannot take pathspecs.
+	Instead, all non-option arguments are concatenated to form the stash
+	message.
 
 list [<options>]::