build: use default value of the enable_widevine flag

build/args/all.gn

@@ -6,7 +6,6 @@ root_extra_deps = [ "//electron" ]
 v8_promise_internal_field_count = 1
 v8_typed_array_max_size_in_heap = 0
 
-enable_widevine = true
 enable_cdm_host_verification = false
 proprietary_codecs = true
 ffmpeg_branding = "Chrome"