fix spurious indent and newlines in rendering of nkRecList (#23121)

Rendering of `nkRecList` produces an indent and adds a new line at the
end. However for things like case object `of`/`else` branches or `when`
branches this is already done, so this produces 2 indents and an extra
new line. Instead, just add an indent in the place where the indent that
`nkRecList` produces is needed, for the rendering of the final node of
`nkObjectTy`. There doesn't seem to be a need to add the newline.

Before:

```nim
case x*: bool
of true:
    y*: int

of false:
  nil
```

After:

```nim
case x*: bool
of true:
  y*: int
of false:
  nil
```

(cherry picked from commit fc49c6e3ba)

lib/core/macros.nim

@@ -347,8 +347,7 @@ proc getTypeImpl*(n: NimNode): NimNode {.magic: "NGetType", noSideEffect.} =
       newLit(x.getTypeImpl.repr)
     let t = """
 object
-  arr: array[0 .. 3, float32]
-"""
+  arr: array[0 .. 3, float32]"""
     doAssert(dumpTypeImpl(a) == t)
     doAssert(dumpTypeImpl(b) == t)
     doAssert(dumpTypeImpl(c) == t)