fix wrong instance of check in DocHashtagReference #1024

Author: Haehnchen

src/fr/adrienbrault/idea/symfony2plugin/util/DocHashTagReferenceContributor.java

@@ -196,7 +196,7 @@ public boolean isValid() {
             }
 
             PsiElement resolvedReference = psiReference.resolve();
-            if (!(resolvedReference instanceof Function)) {
+            if (!(resolvedReference instanceof Method)) {
                 return false;
             }