build: disable Vulkan support by default (#17789)

Is was enabled in
https://chromium.googlesource.com/chromium/src.git/+/327326656f2c8c45ecb0ff4675e5c577e7c275ef
which landed in 69.0.3460.0

Vulkan support would require a command line parameter "--enable-vulkan"
to be passes to a binary to be enabled anyway,
so this change doesn't actual alter the current behaviour of Electron.

(cherry picked from commit e05e45d62d5b951c2cf4f9122fff3a18e5377a6f)

build/args/all.gn

@@ -8,6 +8,7 @@ v8_embedder_string = "-electron.0"
 
 enable_cdm_host_verification = false
 enable_extensions = false
+enable_vulkan = false
 proprietary_codecs = true
 ffmpeg_branding = "Chrome"