SubmittingPatches: remove dq from commit reference

SubmittingPatches: remove dq from commit reference

Quoting SZEDER Gábor[1],

	SubmittingPatches is simply wrong: our de-facto standard format for
	referencing other commits does not enclose the subject in a pair of
	double-quotes:

	  $ git log v2.24.0 |grep -E '[0-9a-f]{7} \("' |wc -l
	  785
	  $ git log v2.24.0 |grep -E '[0-9a-f]{7} \([^"]' |wc -l
	  2276

	Those double-quotes don't add any value to the references, but they
	result in weird looking references for 1083 of our commits whose
	subject lines happen to end with double-quotes, e.g.:

	  f23a465132 ("hashmap_get{,_from_hash} return "struct hashmap_entry *"", 2019-10-06)

	and without those unnecessary pair of double-quotes we would have
	~3000 more commits whose summary would fit on a single line.

Remove references to the enclosing double-quotes from SubmittingPatches
since our de-facto standard for referencing commits does not actually
use them.

[1]: cf. <20191114011048.GS4348@szeder.dev>

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>