UI: Switch RecFormat to RecFormat2

Commit f1223ca566
(UI: Set fragmented MP4/MOV as default for beta/rc)
changed RecFormat to RecFormat2.
This conflicts with the use of RecFormat introduced in
d18b38e784
(UI: Enable multiple audio tracks in Simple Output recording).
This fixes the issue.
An unused var is also removed.

Signed-off-by: pkv <pkv@obsproject.com>
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