Fixes parsing and setting step variables.

Code change suggested by @amritpal-singh-98

python/semantic_kernel/planning/plan.py

@@ -402,19 +402,17 @@ def get_next_step_variables(self, variables: ContextVariables, step: "Plan") ->
             elif param.name in self._state and (self._state[param.name] is not None and self._state[param.name] != ""):
                 step_variables.set(param.name, self._state[param.name])
 
-        for param_var in step.parameters.variables:
-            if param_var in step_variables:
+        for param_name, param_val in step.parameters.variables.items():
+            if param_name in step_variables:
                 continue
 
-            expanded_value = self.expand_from_variables(variables, param_var)
-            if expanded_value.lower() == param_var.lower():
-                step_variables.set(param_var, step.parameters.variables[param_var])
-            elif param_var in variables:
-                step_variables.set(param_var, variables[param_var])
-            elif param_var in self._state:
-                step_variables.set(param_var, self._state[param_var])
+            if param_name in variables:
+                step_variables.set(param_name, param_val)
+            elif param_name in self._state:
+                step_variables.set(param_name, self._state[param_name])
             else:
-                step_variables.set(param_var, expanded_value)
+                expanded_value = self.expand_from_variables(variables, param_val)
+                step_variables.set(param_name, expanded_value)
 
         for item in variables.variables:
             if item not in step_variables: