Cocoa: don't call non-existent NSWindow setFrameSize

Cocoa: don't call non-existent NSWindow setFrameSize

Commit 140579cb3ef676aa3a7c3fc322ddfcc6ec1b70f2 changed a setFrame call
in propagateSizeHints() to setFrameSize, which doesn't exist in
NSWindow. Change it back to setFrame.

Spotted due to this objc warning:

qcocoawindow.mm:232:9: warning: instance method '-setFrameSize:display:'
      not found (return type defaults to 'id')
     [m_nsWindow setFrameSize : NSMakeSize(baseSize.width(),...
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~...

Change-Id: Ieb7e022694ced7e59c07fdd2fc53048dab1e93c7
Reviewed-by: Morten Johan Sørvig <morten.sorvig@nokia.com>