plugins: Set missed default bitrates to 6000 kbps

[mihawk90]

Description

#9442 efca325 already increased the default bitrate for various encoders. However, some were missed and this PR fills the gap:

• Mac-VT
• OpenH264
• Texture AMF
• VAAPI

Note I wasn't sure about the Texture AMF one because there's 4 occurrences (2 for AVC, 2 for HEVC). But I think one each is for new setups and one for migrating existing setups?

There's also one more in nvenc-compat, but the comment made me think this is not used for new setups anymore and just used for legacy configs that were never upgraded? Let me know if it should still be adjusted.

obs-studio/plugins/obs-nvenc/nvenc-compat.c

Lines 103 to 106 in 0b12296

	static void nvenc_defaults_base(enum codec_type codec, obs_data_t *settings)
	{
	/* Defaults from legacy FFmpeg encoder */
	obs_data_set_default_int(settings, "bitrate", 2500);

Motivation and Context

Noticed in unrelated testing that VAAPI was still defaulting to 2500, fixed it and found other occurrences of the same.

How Has This Been Tested?

Checked VAAPI and OpenH264, both defaulted to 6000.
Can't test Mac-VT and Tex-AMF.

Types of changes

• Tweak (non-breaking change to improve existing functionality)

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.

[RytoEX]

Good catch.