Incorrect diagnostic message in TS2814

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### 🔎 Search Terms

2814, function body

### 🕗 Version & Regression Information

- regression at `v4.4.4`.

### ⏯ Playground Link

https://www.typescriptlang.org/play/?ts=4.4.4#code/MYGwhgzhAEBiD29oG9oChqegIzAJwEYAKAShWgF80q0AzAVwDtgAXAS3kbkVIG40A9AIB+APWgBRAEpSA8lIBccJqw5cA7mxYALHPAAmbAKYxgYLpxABPaAFsjeAOZHomndFCQIJ6DrAtofBcwW2xjRhYAOiA

### 💻 Code

```ts
// tests/cases/compiler/callOverloads1.ts

class Foo {
bar1() { }
}

function Foo();
//~^ error report: Function with bodies can only merge with classes that are ambient.
```

### 🙁 Actual behavior

The `function Foo` actually has no body (it's just a declaration), yet the error message says "Function with bodies...", which may be a bit confusing.

### 🙂 Expected behavior

Either show a hint like "Only functions can merge with ambient classes," or suppress the error report for functions without a body because `class Foo` will report `Class declaration cannot implement overload list for 'Foo'`.

### Additional information about the issue

_No response_

Start with tests/cases/compiler/callOverloads1.ts and reproduce the TS2814 diagnostic using the provided Playground example. Trace the diagnostic for a function declaration merged with a class, then choose and validate the reported-message or suppression behavior described in the issue. Update the compiler test expectations so the incorrect wording is no longer accepted.

Written by the indexing model from the issue text.