libobs: Fix missing started signal upon second start of delayed output

[tt2468]

Description

If an output has delay enabled and is gracefully stopped once, upon startup a second time, it will not send the started signal. This is due to obs_output_signal_stop() pre-emtively setting delay_active to false. It is later set to false in
obs_output_end_data_capture_internal(), so this logic is not needed anyway.

When the encoder is then started a second time, output->delay_capturing will still be true, resulting in begin_delayed_capture() returning early and not firing the started signal.

Motivation and Context

I was testing other changes and measuring the various signals of outputs, and noticed that when I performed the reproduction steps above, I wasn't getting a started signal.

How Has This Been Tested?

Ubuntu 22.04
WHIP output

Tested every combination of:

• starting/stopping stream
• enabling/disabling stream delay

Repro steps:

• Configure delayed RTMP stream encoder in OBS
• Enable obs-websocket debug logging
• Start stream to a server
  • You should see a starting then a started event
• Stop stream gracefully (allowing delay to play out before stopping)
• Start stream again
  • You should see a starting event but no started event

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.