Remove unused classnames dependency from react-dev-overlay (#32487)

It seems that the classnames dependency is not referenced in the react-dev-overlay code.

packages/react-dev-overlay/package.json

@@ -19,7 +19,6 @@
     "@babel/code-frame": "7.12.11",
     "anser": "1.4.9",
     "chalk": "4.0.0",
-    "classnames": "2.2.6",
     "css.escape": "1.5.1",
     "data-uri-to-buffer": "3.0.1",
     "platform": "1.3.6",

yarn.lock

@@ -7071,10 +7071,6 @@ class-utils@^0.3.5:
     isobject "^3.0.0"
     static-extend "^0.1.1"
 
-classnames@2.2.6:
-  version "2.2.6"
-  resolved "https://registry.yarnpkg.com/classnames/-/classnames-2.2.6.tgz#43935bffdd291f326dad0a205309b38d00f650ce"
-
 clean-stack@^2.0.0:
   version "2.2.0"
   resolved "https://registry.yarnpkg.com/clean-stack/-/clean-stack-2.2.0.tgz#ee8472dbb129e727b31e8a10a427dee9dfe4008b"