Revert "Introduce explicit copy (#15330)" (#15346)

This reverts commit a3e9cc5.

compiler/injectdestructors.nim

@@ -408,7 +408,7 @@ proc passCopyToSink(n: PNode; c: var Con; s: var Scope): PNode =
     if isLValue(n) and not isCapturedVar(n) and n.typ.skipTypes(abstractInst).kind != tyRef and c.inSpawn == 0:
       message(c.graph.config, n.info, hintPerformance,
         ("passing '$1' to a sink parameter introduces an implicit copy; " &
-         "if possible, rearrange your program's control flow to prevent it or use 'copy($1)' to hint the compiler it is intentional") % $n)
+        "if possible, rearrange your program's control flow to prevent it") % $n)
   else:
     if c.graph.config.selectedGC in {gcArc, gcOrc}:
       assert(not containsGarbageCollectedRef(n.typ))

lib/system.nim

@@ -264,11 +264,6 @@ proc move*[T](x: var T): T {.magic: "Move", noSideEffect.} =
   result = x
   wasMoved(x)
 
-func copy*[T](x: T): T {.inline.} =
-  ## make explicit copy of the argument `x`, used to signal to the compiler
-  ## the copy is intentional
-  result = x
-
 type
   range*[T]{.magic: "Range".}         ## Generic type to construct range types.
   array*[I, T]{.magic: "Array".}      ## Generic type to construct