Drop redundant ./Box export (covered by ./* wildcard)

Author: Janpot

packages/mui-system/package.json

@@ -83,7 +83,6 @@
   },
   "exports": {
     ".": "./src/index.js",
-    "./Box": "./src/Box/index.js",
     "./createTheme": "./src/createTheme/index.js",
     "./RtlProvider": "./src/RtlProvider/index.js",
     "./styleFunctionSx": "./src/styleFunctionSx/index.js",