Update clsx requirement in /packages/material-ui-lab (#44)

Updates the requirements on [clsx](https://github.com/lukeed/clsx) to permit the latest version.
- [Release notes](https://github.com/lukeed/clsx/releases)
- [Commits](lukeed/clsx@v1.0.2...v1.0.4)

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

packages/material-ui-lab/package.json

@@ -41,7 +41,7 @@
   "dependencies": {
     "@babel/runtime": "^7.5.5",
     "@material-ui/utils": "^4.1.0",
-    "clsx": "^1.0.2",
+    "clsx": "^1.0.4",
     "prop-types": "^15.7.2",
     "warning": "^4.0.3"
   },