doc: git-add: remove options from SYNOPSIS

Motivations for this change:

1. Listing a huge number of options is visually overwhelming when
   opening a man page for an unfamiliar command. It makes it harder
   to understand the command's core syntax, like `git add <filename>`
2. For options which can be passed independently of any other options,
   including them in the SYNOPSIS does not add any information which you
   can't already get from reading the OPTIONS section. `git add` has
   some mutually exclusive options, namely:
   [--[no-]all | -A | --[no-]ignore-removal | [--update | -u]]
   but personally I already find that line so hard to parse that
   removing it doesn't remove a lot of information
3. Some man pages already take this approach, like `git rebase` and
   `git status`

Author: jvns

Documentation/git-add.adoc

@@ -8,11 +8,7 @@ git-add - Add file contents to the index
 SYNOPSIS
 --------
 [synopsis]
-git add [--verbose | -v] [--dry-run | -n] [--force | -f] [--interactive | -i] [--patch | -p]
-	[--edit | -e] [--[no-]all | -A | --[no-]ignore-removal | [--update | -u]] [--sparse]
-	[--intent-to-add | -N] [--refresh] [--ignore-errors] [--ignore-missing] [--renormalize]
-	[--chmod=(+|-)x] [--pathspec-from-file=<file> [--pathspec-file-nul]]
-	[--] [<pathspec>...]
+git add [<options>] [--] [<pathspec>...]
 
 DESCRIPTION
 -----------