Enable Instant Tethering by default.

This will now be enabled by default, but disabled on specific
problematic boards. See go/tethering-client-expansion for
details.

Change-Id: Ia9988e3d6ad3b249f9a80d78b8f8607129218137
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2222296
Commit-Queue: Max Li <themaxli@chromium.org>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774405}

chromeos/constants/chromeos_features.cc

@@ -243,7 +243,7 @@ const base::Feature kVirtualKeyboardFloatingDefault{
 
 // Enables or disables Instant Tethering on Chrome OS.
 const base::Feature kInstantTethering{"InstantTethering",
-                                      base::FEATURE_DISABLED_BY_DEFAULT};
+                                      base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables "Linux and Chrome OS" support. Allows a Linux version of Chrome
 // ("lacros-chrome") to run as a Wayland client with this instance of Chrome