Bump xterm-addon-webgl in /terminus-terminal

Bumps [xterm-addon-webgl](https://github.com/xtermjs/xterm.js) from 0.6.0-beta.3 to 0.7.0-beta.4.
- [Release notes](https://github.com/xtermjs/xterm.js/releases)
- [Commits](https://github.com/xtermjs/xterm.js/commits)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

terminus-terminal/package.json

@@ -33,7 +33,7 @@
     "xterm-addon-search": "^0.5.0",
     "xterm-addon-serialize": "^0.1.1",
     "xterm-addon-unicode11": "^0.1.1",
-    "xterm-addon-webgl": "^0.6.0-beta.2",
+    "xterm-addon-webgl": "^0.7.0-beta.4",
     "zmodem.js": "^0.1.9"
   },
   "peerDependencies": {