Remove unnecessary WebRTC shim (MetaMask#7886)

The WebRTC spec is fairly stable these days, particularly among the
browsers we support. We don't need this shim for anything. I'm guessing
it may have been added primarily with IE in mind.

package.json

@@ -196,7 +196,6 @@
     "textarea-caret": "^3.0.1",
     "valid-url": "^1.0.9",
     "web3-stream-provider": "^4.0.0",
-    "webrtc-adapter": "^6.3.0",
     "xtend": "^4.0.1"
   },
   "devDependencies": {

ui/app/components/app/modals/qr-scanner/qr-scanner.component.js

@@ -1,7 +1,6 @@
 import React, { Component } from 'react'
 import PropTypes from 'prop-types'
 import { BrowserQRCodeReader } from '@zxing/library'
-import 'webrtc-adapter'
 import Spinner from '../../../ui/spinner'
 import WebcamUtils from '../../../../../lib/webcam-utils'
 import PageContainerFooter from '../../../ui/page-container/page-container-footer/page-container-footer.component'

yarn.lock

@@ -25104,13 +25104,6 @@ rst-selector-parser@^2.2.3:
     lodash.flattendeep "^4.4.0"
     nearley "^2.7.10"
 
-rtcpeerconnection-shim@^1.2.10:
-  version "1.2.13"
-  resolved "https://registry.yarnpkg.com/rtcpeerconnection-shim/-/rtcpeerconnection-shim-1.2.13.tgz#326e316b06e8b96b40f7558c8f582b86dd2c1b46"
-  integrity sha512-Xz4zQLZNs9lFBvqbaHGIjLWtyZ1V82ec5r+WNEo7NlIx3zF5M3ytn9mkkfYeZmpE032cNg3Vvf0rP8kNXUNd9w==
-  dependencies:
-    sdp "^2.6.0"
-
 rtlcss@^2.4.0:
   version "2.4.0"
   resolved "https://registry.yarnpkg.com/rtlcss/-/rtlcss-2.4.0.tgz#482ea28f2b9fe06dd0ab3057997be9af13da84c1"
@@ -25450,11 +25443,6 @@ scss-tokenizer@^0.2.3:
     js-base64 "^2.1.8"
     source-map "^0.4.2"
 
-sdp@^2.6.0, sdp@^2.7.0:
-  version "2.8.0"
-  resolved "https://registry.yarnpkg.com/sdp/-/sdp-2.8.0.tgz#8d914a733b1c19b6d8fd36ba6cd2dfbfbd668b8a"
-  integrity sha512-wRSES07rAwKWAR7aev9UuClT7kdf9ZTdeUK5gTgHue9vlhs19Fbm3ccNEGJO4y2IitH4/JzS4sdzyPl6H2KQLw==
-
 secp256k1@^3.0.1, secp256k1@^3.6.1, secp256k1@^3.6.2, secp256k1@^3.7.1:
   version "3.7.1"
   resolved "https://registry.yarnpkg.com/secp256k1/-/secp256k1-3.7.1.tgz#12e473e0e9a7c2f2d4d4818e722ad0e14cc1e2f1"
@@ -29544,14 +29532,6 @@ webpack@^4.28.0, webpack@^4.32.0:
     watchpack "^1.5.0"
     webpack-sources "^1.3.0"
 
-webrtc-adapter@^6.3.0:
-  version "6.3.2"
-  resolved "https://registry.yarnpkg.com/webrtc-adapter/-/webrtc-adapter-6.3.2.tgz#7e616e27defe31968b22b01b902db0d0e68ae786"
-  integrity sha512-7pFMXpZCka7ScIQyk8Wo+fOr3OlKLtGd6YHqkHVT74zerpY2Siyds8sxsmkE0bNqsi/J1b0vDzN7WpB34dQzAA==
-  dependencies:
-    rtcpeerconnection-shim "^1.2.10"
-    sdp "^2.7.0"
-
 "webrtcsupport@github:ipfs/webrtcsupport":
   version "2.2.0"
   resolved "https://codeload.github.com/ipfs/webrtcsupport/tar.gz/0669f576582c53a3a42aa5ac014fcc5966809615"