update to IDLs version 3.43.1

[devoncarew]

• update to IDLs version 3.43.1

Update to the latest IDLs. We need to generate the library for the css-view-transitions IDL as the html idl references its types (otherwise we wouldn't generate css-view-transitions, as the ViewTransition API is standards-track but only supported by chrome).

As we are emitting some code that we otherwise wouldn't, it could be useful to emit some dartdoc or annotations which clarified on which platforms an API was available.

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[kevmoo]

[devoncarew]

landing; cc @srujzs