runtime: remove no-op slice operation in Caller

rpc was an array prior to CL 152537, so it was necessary to slice
it since callers accepts a slice. Now that rpc is already a slice,
slicing it is no longer required.

Change-Id: Ie646ef5e494323c9fb58f3a24f942e3b1ff639ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/579016
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

src/runtime/extern.go

@@ -297,7 +297,7 @@ import (
 // call. The boolean ok is false if it was not possible to recover the information.
 func Caller(skip int) (pc uintptr, file string, line int, ok bool) {
 	rpc := make([]uintptr, 1)
-	n := callers(skip+1, rpc[:])
+	n := callers(skip+1, rpc)
 	if n < 1 {
 		return
 	}