Travis: Pin Emscripten version to 1.39.19
Travis: Pin Emscripten version to 1.39.19

1.39.20 dropped support for the no-embedded mode we use since #39168,
as our detection logic hasn't been fixed yet to support the embedded
mode.

honix/godot,Paulloz/godot,Zylann/godot,Faless/godot,vnen/godot,akien-mga/godot,josempans/godot,MarianoGnu/godot,DmitriySalnikov/godot,MarianoGnu/godot,Paulloz/godot,BastiaanOlij/godot,Zylann/godot,pkowal1982/godot,guilhermefelipecgs/godot,guilhermefelipecgs/godot,DmitriySalnikov/godot,DmitriySalnikov/godot,godotengine/godot,firefly2442/godot,DmitriySalnikov/godot,Zylann/godot,Shockblast/godot,firefly2442/godot,godotengine/godot,honix/godot,Shockblast/godot,sanikoyes/godot,Zylann/godot,firefly2442/godot,vkbsb/godot,honix/godot,godotengine/godot,firefly2442/godot,vnen/godot,godotengine/godot,vnen/godot,Paulloz/godot,Faless/godot,honix/godot,firefly2442/godot,ZuBsPaCe/godot,Paulloz/godot,honix/godot,ZuBsPaCe/godot,MarianoGnu/godot,Valentactive/godot,Shockblast/godot,sanikoyes/godot,josempans/godot,Faless/godot,ZuBsPaCe/godot,ZuBsPaCe/godot,DmitriySalnikov/godot,MarianoGnu/godot,akien-mga/godot,akien-mga/godot,Valentactive/godot,BastiaanOlij/godot,godotengine/godot,josempans/godot,sanikoyes/godot,Valentactive/godot,guilhermefelipecgs/godot,BastiaanOlij/godot,akien-mga/godot,vnen/godot,vkbsb/godot,firefly2442/godot,Paulloz/godot,godotengine/godot,BastiaanOlij/godot,BastiaanOlij/godot,sanikoyes/godot,ZuBsPaCe/godot,vnen/godot,Shockblast/godot,Faless/godot,Shockblast/godot,josempans/godot,Shockblast/godot,pkowal1982/godot,guilhermefelipecgs/godot,sanikoyes/godot,guilhermefelipecgs/godot,vkbsb/godot,akien-mga/godot,MarianoGnu/godot,Zylann/godot,Faless/godot,guilhermefelipecgs/godot,firefly2442/godot,Valentactive/godot,pkowal1982/godot,Zylann/godot,Shockblast/godot,vnen/godot,Paulloz/godot,BastiaanOlij/godot,guilhermefelipecgs/godot,Zylann/godot,vnen/godot,akien-mga/godot,Valentactive/godot,Paulloz/godot,honix/godot,vnen/godot,vkbsb/godot,MarianoGnu/godot,josempans/godot,akien-mga/godot,akien-mga/godot,sanikoyes/godot,Shockblast/godot,pkowal1982/godot,Faless/godot,josempans/godot,ZuBsPaCe/godot,guilhermefelipecgs/godot,pkowal1982/godot,godotengine/godot,pkowal1982/godot,Faless/godot,vkbsb/godot,ZuBsPaCe/godot,Zylann/godot,Valentactive/godot,Faless/godot,godotengine/godot,vkbsb/godot,DmitriySalnikov/godot,sanikoyes/godot,ZuBsPaCe/godot,BastiaanOlij/godot,Valentactive/godot,vkbsb/godot,DmitriySalnikov/godot,BastiaanOlij/godot,sanikoyes/godot,firefly2442/godot,Valentactive/godot,josempans/godot,josempans/godot,MarianoGnu/godot,pkowal1982/godot,MarianoGnu/godot,vkbsb/godot,pkowal1982/godot