net/netip: add missing ) in ParsePrefix errors

The existing error messages didn't add right parenthesis ')' properly
leading to improper formation of error messages.

Fixes #53283

Change-Id: Iadf9b8059403efa07e39716a81fab68cd10b7f87
Reviewed-on: https://go-review.googlesource.com/c/go/+/411015
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Damien Neil <dneil@google.com>

src/net/netip/netip.go

@@ -1310,14 +1310,14 @@ func ParsePrefix(s string) (Prefix, error) {
 	bitsStr := s[i+1:]
 	bits, err := strconv.Atoi(bitsStr)
 	if err != nil {
-		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + ": bad bits after slash: " + strconv.Quote(bitsStr))
+		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): bad bits after slash: " + strconv.Quote(bitsStr))
 	}
 	maxBits := 32
 	if ip.Is6() {
 		maxBits = 128
 	}
 	if bits < 0 || bits > maxBits {
-		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + ": prefix length out of range")
+		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): prefix length out of range")
 	}
 	return PrefixFrom(ip, bits), nil
 }