Fix IDL generation after 264293@main when MODERN_MEDIA_CONTROLS is off

[mokjasmine]

e660f99

Fix IDL generation after 264293@main when MODERN_MEDIA_CONTROLS is off
https://bugs.webkit.org/show_bug.cgi?id=257168

Reviewed by Don Olmstead.

Guard `SourceType` with a `MODERN_MEDIA_CONTROLS` conditional.

* Source/WebCore/Modules/mediacontrols/MediaControlsHost.idl:

Canonical link: https://commits.webkit.org/264387@main

ebb89d5

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	🧪 wpe-wk2
✅ 🧪 webkitperl	🧪 ios-wk2	🧪 api-mac	✅ 🛠 gtk
	🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	🧪 gtk-wk2
	🧪 api-ios	🧪 mac-wk2	🧪 api-gtk
	✅ 🛠 tv	🧪 mac-AS-debug-wk2
	🛠 tv-sim
	🛠 watch
✅ 🛠 🧪 unsafe-merge	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash ebb89d5)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	🧪 wpe-wk2
✅ 🧪 webkitperl	🧪 ios-wk2	🧪 api-mac	✅ 🛠 gtk
	🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	🧪 gtk-wk2
	🧪 api-ios	🧪 mac-wk2	🧪 api-gtk
	✅ 🛠 tv	🧪 mac-AS-debug-wk2
	🛠 tv-sim
	🛠 watch
✅ 🛠 🧪 unsafe-merge	✅ 🛠 watch-sim

[webkit-commit-queue]

Committed 264387@main (e660f99): https://commits.webkit.org/264387@main

Reviewed commits have been landed. Closing PR #14220 and removing active labels.