Fix mistake in chrome.proxy documentation.

The hostname is just a host, not a URI. IPs are also fine.

Bug: none
Change-Id: I6e51f3a1086d10b68b2c5d34ca675f1e48a2aa38
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1639147
Commit-Queue: David Benjamin <davidben@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Auto-Submit: David Benjamin <davidben@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665303}

chrome/common/extensions/api/proxy.json

@@ -23,7 +23,7 @@
         "description": "An object encapsulating a single proxy server's specification.",
         "properties": {
           "scheme": {"$ref": "Scheme", "optional": true, "description": "The scheme (protocol) of the proxy server itself. Defaults to 'http'."},
-          "host": {"type": "string", "description": "The URI of the proxy server. This must be an ASCII hostname (in Punycode format). IDNA is not supported, yet."},
+          "host": {"type": "string", "description": "The hostname or IP address of the proxy server. Hostnames must be in ASCII (in Punycode format). IDNA is not supported, yet."},
           "port": {"type": "integer", "optional": true, "description": "The port of the proxy server. Defaults to a port that depends on the scheme."}
         }
       },