runtime: remove useless empty string literal

Assumingly this appears to have been a bug in c2go, as this appeared in
https://go.dev/cl/172260043.

Change-Id: I8477ec226ffb31268b9c479af13b0fcf401dbeec
Reviewed-on: https://go-review.googlesource.com/c/go/+/418276
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Run-TryBot: Michael Pratt <[email protected]>

Author: prattmic

src/runtime/proc.go

@@ -5459,7 +5459,7 @@ func schedtrace(detailed bool) {
 		if lockedg != nil {
 			id3 = lockedg.goid
 		}
-		print("  M", mp.id, ": p=", id1, " curg=", id2, " mallocing=", mp.mallocing, " throwing=", mp.throwing, " preemptoff=", mp.preemptoff, ""+" locks=", mp.locks, " dying=", mp.dying, " spinning=", mp.spinning, " blocked=", mp.blocked, " lockedg=", id3, "\n")
+		print("  M", mp.id, ": p=", id1, " curg=", id2, " mallocing=", mp.mallocing, " throwing=", mp.throwing, " preemptoff=", mp.preemptoff, " locks=", mp.locks, " dying=", mp.dying, " spinning=", mp.spinning, " blocked=", mp.blocked, " lockedg=", id3, "\n")
 	}
 
 	forEachG(func(gp *g) {