EvalState::resetFileCache: clear parse cache as well as eval cache

Fixes #2546.

(at least the basic reproduction I've been testing)

src/libexpr/eval.cc

@@ -757,6 +757,7 @@ void EvalState::evalFile(const Path & path_, Value & v)
 void EvalState::resetFileCache()
 {
     fileEvalCache.clear();
+    fileParseCache.clear();
 }