refactoring: square funktion test rename

src/test/test_funktionen.c

@@ -22,7 +22,7 @@ void test_squareRoot(void) {
     TEST_ASSERT_EQUAL_FLOAT(3.0, result);
 }
 
-void test_cube(void) {
+void test_cube_for_2(void) {
     float result = cube(2.0);
     TEST_ASSERT_EQUAL_FLOAT(8.0, result);
 }