fix(curriculum): make test stricter in case coverter project (freeCodeCamp#57883)

Author: Dario-DC

curriculum/challenges/english/07-scientific-computing-with-python/learn-list-comprehension-by-building-a-case-converter-program/657f456223b8c1187b461987.md

@@ -50,7 +50,8 @@ Your list comprehension should evaluate `'_' + char.lower()` for each `char` in
 ```js
 ({ 
     test: () => assert(runPython(`
-    _Node(_code).find_function("convert_to_snake_case").find_variable("snake_cased_char_list").find_comp_expr().is_equivalent("'_' + char.lower()")
+    target_var = _Node(_code).find_function("convert_to_snake_case").find_variable("snake_cased_char_list")
+    target_var.find_comp_expr().is_equivalent("'_' + char.lower()") and len(target_var.find_comp_ifs()) == 0
     `)) 
 })
 ```