LibJS: Remove using-declaration.js from .prettierignore

This is the second and final commit to remove using-declaration from
.prettierignore. While there is standard formatting changes here, there
is also scoping changes for the 'using' declarations due to the
following error:

Libraries/LibJS/Tests/using-declaration.js: SyntaxError:
Using declaration cannot appear in the top level when source
type is `script` or in the bare case statement.

.prettierignore

@@ -2,9 +2,6 @@ Libraries/LibJS/Tests/invalid-lhs-in-assignment.js
 Libraries/LibJS/Tests/unicode-identifier-escape.js
 Libraries/LibJS/Tests/modules/failing.mjs
 
-# FIXME: Remove once prettier is updated to support using declarations.
-Libraries/LibJS/Tests/using-declaration.js
-
 Tests/LibWeb/Crash/wpt-import/
 Tests/LibWeb/Ref/input/wpt-import
 Tests/LibWeb/Text/input/wpt-import

Libraries/LibJS/Tests/using-declaration.js

@@ -307,9 +307,14 @@ describe("works in a bunch of scopes", () => {
         }
 
         switch (2) {
-            case 3:
+            case 3: {
-                using notDisposed = { [Symbol.dispose]() { expect().fail("not-disposed 1"); } };
+                using notDisposed = {
-            case 2:
+                    [Symbol.dispose]() {
+                        expect().fail("not-disposed 1");
+                    },
+                };
+            }
+            case 2: {
                 expect(disposeFull).toEqual([]);
                 using a = pusher("a");
                 expect(disposeFull).toEqual([]);
@@ -318,22 +323,35 @@ describe("works in a bunch of scopes", () => {
                 expect(disposeFull).toEqual([]);
                 expect(b.val).toBe("b");
 
-                expect(disposeInner).toBeFalse();
-                // fallthrough
-            case 1: {
-                expect(disposeFull).toEqual([]);
-                expect(disposeInner).toBeFalse();
-
-                using inner = { [Symbol.dispose]() { disposeInner = true; } }
-
                 expect(disposeInner).toBeFalse();
             }
+            // fallthrough
+            case 1:
+                {
+                    expect(disposeFull).toEqual([]);
+                    expect(disposeInner).toBeFalse();
+
+                    using inner = {
+                        [Symbol.dispose]() {
+                            disposeInner = true;
+                        },
+                    };
+
+                    expect(disposeInner).toBeFalse();
+                }
                 expect(disposeInner).toBeTrue();
-                using c = pusher("c");
+                {
-                expect(c.val).toBe("c");
+                    using c = pusher("c");
+                    expect(c.val).toBe("c");
+                }
                 break;
-            case 0:
+            case 0: {
-                using notDisposed2 = { [Symbol.dispose]() { expect().fail("not-disposed 2"); } };
+                using notDisposed2 = {
+                    [Symbol.dispose]() {
+                        expect().fail("not-disposed 2");
+                    },
+                };
+            }
         }
 
         expect(disposeInner).toBeTrue();