Revert #289135: lua*: support relative modules even when there are sy…

…stem modules

This reverts commit ca6452f.
Regressions appeared and they need time to get resolved; see:
#289135 (comment)

pkgs/development/interpreters/lua-5/hooks/setup-hook.sh

@@ -22,11 +22,6 @@ addToLuaSearchPathWithCustomDelimiter() {
   # export only if we haven't already got this dir in the search path
   if [[ ${!varName-} == *"$absPattern"* ]]; then return; fi
 
-  # if the path variable has not yet been set, initialize it to ";;"
-  # this is a magic value that will be replaced by the default,
-  # allowing relative modules to be used even when there are system modules.
-  if [[ -v "${varName}" ]]; then export "${varName}=;;"; fi
-
   export "${varName}=${!varName:+${!varName};}${absPattern}"
 }