win_environment: remove uneeded required_by entry in spec (#54369)

lib/ansible/modules/windows/win_environment.ps1

@@ -12,9 +12,6 @@ $spec = @{
         state = @{ type = "str"; choices = "absent", "present"; default = "present" }
         value = @{ type = "str" }
     }
-    required_by = @{
-        present = @("value")
-    }
     required_if = @(,@("state", "present", @("value")))
     supports_check_mode = $true
 }