revert #23436; remove workaround (#23653)

revert #23436

Author: ringabout

lib/system/indices.nim

@@ -80,8 +80,6 @@ proc `[]`*[T, U: Ordinal](s: string, x: HSlice[T, U]): string {.inline, systemRa
   ##   var s = "abcdef"
   ##   assert s[1..3] == "bcd"
   ##   ```
-  # Workaround bug #22852
-  result = ""
   let a = s ^^ x.a
   let L = (s ^^ x.b) - a + 1
   result = newString(L)