Respect $wgApiFrameOptions in formatted API output mode

This restores the pre- d25cb992 behaviour. Apparently UploadWizard's
flickr module relies on this (Which seems rather wrong, but
regardless I still think api handling of $wgApiFrameOptions should
extend to the "fm" modes.)

Note: If $wgBreakFrames is true, then frames will still be broken.
Although this is a change from prior behaviour, it makes sense
to me that $wgBreakFrames would not allow the human readable output
of the API be frammed.

Bug: 72340
Change-Id: Ia61a4698f7044acfcd7339207590d9333f4100cb
Merge "Respect $wgApiFrameOptions in formatted API output mode"