Correct identification of in/instanceof identifiers (#20019)

Co-authored-by: fisker Cheung <lionkay@gmail.com>

changelog_unreleased/javascript/20019.md

@@ -0,0 +1,22 @@
+#### Avoid unnecessary semicolons before private members named `#in` or `#instanceof` (#20019 by @cellison-figma)
+
+<!-- prettier-ignore -->
+```js
+// Input
+class Graph {
+  #nodes = {};
+  #in = {};
+}
+
+// Prettier stable (--parser oxc --no-semi)
+class Graph {
+  #nodes = {};
+  #in = {}
+}
+
+// Prettier main (--parser oxc --no-semi)
+class Graph {
+  #nodes = {}
+  #in = {}
+}
+```