Fix duplicate definition error in private class methods (#9453)

packages/babel-plugin-proposal-private-methods/test/fixtures/private-method/scopable/exec.js

@@ -0,0 +1,17 @@
+class Foo {
+  #privateMethodA() {
+    const i = 40;
+    return i;
+  }
+
+  #privateMethodB() {
+    const i = 2;
+    return i;
+  }
+
+  publicMethod() {
+    return this.#privateMethodA() + this.#privateMethodB();
+  }
+}
+
+expect((new Foo).publicMethod()).toEqual(42);