Revert "config/security: Add HOME to default exec env var whitelist"

There have been one report in the wild suggesting that this needs to be tested better before doing:

https://discourse.gohugo.io/t/hugo-mod-failing-in-v0-91-1-but-works-in-v0-91-0/36180/5

This reverts commit fca266ebbb.

data/docs.json

@@ -1839,7 +1839,7 @@
           "^postcss$"
         ],
         "osEnv": [
-          "(?i)^(PATH|PATHEXT|APPDATA|HOME|TMP|TEMP|TERM)$"
+          "(?i)^(PATH|PATHEXT|APPDATA|TMP|TEMP|TERM)$"
         ]
       },
       "funcs": {