KCL: No 'let' or 'const' required when declaring vars (#4063)

Previously variable declaration required a keyword, e.g.

```kcl
let x = 4
const x = 4
var x = 4
```

These were all valid, and did the exact same thing. As of this PR, they're all still valid, but the KCL formatter will change them all to just:

```kcl
x = 4
```

which is the new preferred way to declare a constant. 

But the formatter will remove the var/let/const keywords.

Closes https://github.com/KittyCAD/modeling-app/issues/3985

e2e/playwright/testing-camera-movement.spec.ts

@@ -210,7 +210,7 @@ test.describe('Testing Camera Movement', () => {
     // select a plane
     await page.mouse.click(700, 325)
 
-    let code = `const sketch001 = startSketchOn('XY')`
+    let code = `sketch001 = startSketchOn('XY')`
     await expect(u.codeLocator).toHaveText(code)
     await u.closeDebugPanel()