all: remove unnecessary string([]byte) conversion in fmt.Sprintf with %s

Change-Id: I64aab811cbcbfa410817894f1cd1d83f88f27bf6
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/365874
Reviewed-by: Damien Neil <[email protected]>
Trust: Damien Neil <[email protected]>
Trust: Emmanuel Odeke <[email protected]>

Author: odeke-em

internal/encoding/text/decode.go

@@ -381,7 +381,7 @@ func (d *Decoder) currentOpenKind() (Kind, byte) {
 	case '[':
 		return ListOpen, ']'
 	}
-	panic(fmt.Sprintf("Decoder: openStack contains invalid byte %s", string(openCh)))
+	panic(fmt.Sprintf("Decoder: openStack contains invalid byte %c", openCh))
 }
 
 func (d *Decoder) pushOpenStack(ch byte) {

testing/prototest/message.go

@@ -643,7 +643,7 @@ func formatValue(v pref.Value) string {
 		if err != nil {
 			return fmt.Sprintf("<%v>", err)
 		}
-		return fmt.Sprintf("%v{%v}", v.Descriptor().FullName(), string(b))
+		return fmt.Sprintf("%v{%s}", v.Descriptor().FullName(), b)
 	case string:
 		return fmt.Sprintf("%q", v)
 	default: