javascript/Makefile: Change variable to EXPORTED_RUNTIME_METHODS.

EXTRA_EXPORTED_RUNTIME_METHODS is deprecated.
Signed-off-by: Damien George <damien@micropython.org>

ports/javascript/Makefile

@@ -43,7 +43,7 @@ OBJ += $(addprefix $(BUILD)/, $(SRC_SHARED:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
 
 JSFLAGS += -s ASYNCIFY
-JSFLAGS += -s EXPORTED_FUNCTIONS="['_mp_js_init', '_mp_js_init_repl', '_mp_js_do_str', '_mp_js_process_char', '_mp_hal_get_interrupt_char', '_mp_sched_keyboard_interrupt']" -s EXTRA_EXPORTED_RUNTIME_METHODS="['ccall', 'cwrap']" -s --memory-init-file 0 --js-library library.js
+JSFLAGS += -s EXPORTED_FUNCTIONS="['_mp_js_init', '_mp_js_init_repl', '_mp_js_do_str', '_mp_js_process_char', '_mp_hal_get_interrupt_char', '_mp_sched_keyboard_interrupt']" -s EXPORTED_RUNTIME_METHODS="['ccall', 'cwrap']" -s --memory-init-file 0 --js-library library.js
 
 all: $(BUILD)/micropython.js