html5ever: explicitly enable nightly rustc_encodable_decodable feature #3902

Job	Run time
Test codegen backend benchmarks	1m 5s
Test and deploy	3m 3s
Compare page endpoint test	3m 26s
Database Check	1m 1s
Test benchmarks (--include cargo-0.60.0,stm32f4-0.14.0,webrender-2022, Check,Debug,Doc)	5m 49s
Test on Windows	4m 50s
Test benchmarks (--include cargo-0.60.0,stm32f4-0.14.0,webrender-2022, Opt)	5m 29s
Test profiling	3m 32s
Test benchmarks (--exclude cargo-0.60.0,stm32f4-0.14.0,webrender-2022, Check,Debug,Doc)	8m 46s
Test benchmarks (--exclude cargo-0.60.0,stm32f4-0.14.0,webrender-2022, Opt)	8m 10s
Test runtime benchmarks	5m 10s
	50m 21s

Provide feedback