Remove calls for enabling/disabling platform notifications

Disabling proxy config notifications when browser goes in
background was not allowing proxy change listener to process
proxy change events. This was resulting in browser having wrong
proxy settings while user switches to wifi while browser is still
in background. After bringing browser back to foreground
browser was having wrong proxy settings. Fix was to not to disable
platform notifications while in background.

Change-Id: I2c3d9547cfc7d357264401da902e723e44173b69
1 file changed