Remove all v-deep hacks

[nickvergessen]

By "accident" a lot of ::v-deep hacks were added to the CallView.vue.

::v-deep is evil and must ONLY be used if we need to temporarily fix the nextcloud-vue library or overwrite another 3rd party library.
But due to timing constraints all the CSS of calls ended up in the call view instead of the respective Vue component it seems, causing me to waste ~1h trying to find out why the avatar would always be grey in the Video.vue, until I found the ::v-deep in CallView.vue

spreed/src/components/CallView/CallView.vue

Lines 395 to 398 in 714ac2a

	.videoContainer ::v-deep .avatar-container .avatardiv--unknown {
	// Force grey background for guest avatars
	background-color: #b9b9b9 !important;
	}