Fix documentation for core.gitproxy to reflect code

The current implementation of core.gitproxy only operates on
git:// URLs, so the ssh:// examples and custom protocol examples
have been removed or edited.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -101,7 +101,7 @@ Example
 
 	# Proxy settings
 	[core]
-		gitProxy="ssh" for "ssh://kernel.org/"
+		gitProxy="ssh" for "kernel.org"
 		gitProxy=default-proxy ; for the rest
 
 Variables

Documentation/git-config.txt

@@ -214,9 +214,7 @@ Given a .git/config like this:
 
 	; Proxy settings
 	[core]
-		gitproxy="ssh" for "ssh://kernel.org/"
 		gitproxy="proxy-command" for kernel.org
-		gitproxy="myprotocol-command" for "my://"
 		gitproxy=default-proxy ; for all the rest
 
 you can set the filemode to true with
@@ -291,7 +289,7 @@ To actually match only values with an exclamation mark, you have to
 To add a new proxy, without altering any of the existing ones, use
 
 ------------
-% git config core.gitproxy '"proxy" for example.com'
+% git config core.gitproxy '"proxy-command" for example.com'
 ------------