doc: drop "explicitly given" from push.default description

The documentation for push.default mentions that it is used if no
refspec is "explicitly given". Let's drop the notion of "explicit" here,
since it's vague, and just mention that any refspec from anywhere is
sufficient to override this.

I've dropped the mention of "explicitly given" from the definition of
the "nothing" value right below, too. It's close enough to our
clarification that it should be obvious we mean the same type of "given"
here.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/push.txt

@@ -1,14 +1,15 @@
 push.default::
 	Defines the action `git push` should take if no refspec is
-	explicitly given.  Different values are well-suited for
+	given (whether from the command-line, config, or elsewhere).
+	Different values are well-suited for
 	specific workflows; for instance, in a purely central workflow
 	(i.e. the fetch source is equal to the push destination),
 	`upstream` is probably what you want.  Possible values are:
 +
 --
 
 * `nothing` - do not push anything (error out) unless a refspec is
-  explicitly given. This is primarily meant for people who want to
+  given. This is primarily meant for people who want to
   avoid mistakes by always being explicit.
 
 * `current` - push the current branch to update a branch with the same