wasm: remove BINARYEN_METHOD from link line

This has been removed in emscripten compler version 1.38.23 and will
cause building apps to fail.

Change-Id: I7e58053ce06053f6f1d577377b503cabb035bb58
Fixes: QTBUG-73143
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

mkspecs/wasm-emscripten/qmake.conf

@@ -20,7 +20,6 @@ EMCC_COMMON_LFLAGS = \
     -s NO_EXIT_RUNTIME=0 \
     -s ERROR_ON_UNDEFINED_SYMBOLS=1 \
     --bind \
-    -s \"BINARYEN_METHOD=\'native-wasm\'\" \
     -s \"BINARYEN_TRAP_MODE=\'clamp\'\"
 
 # The -s arguments can also be used with release builds,