cmd/gorelease: remove redundant fmt.Sprintf call

setNotValid already accepts a format string and uses
fmt.Sprintf internally so its caller doesn't need to.

Caught by the improved vet check as of CL 707135:

$ go vet ./cmd/gorelease
cmd/gorelease/report.go:271:15: non-constant format string in call to setNotValid

Change-Id: Ic45dbf8c2ed672d5b3356eab802795b81094cf1e
Reviewed-on: https://go-review.googlesource.com/c/exp/+/712780
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
diff --git a/cmd/gorelease/report.go b/cmd/gorelease/report.go
index 3895c98..61b0b1a 100644
--- a/cmd/gorelease/report.go
+++ b/cmd/gorelease/report.go
@@ -268,7 +268,7 @@
 		}
 	}
 	if latestForBaseMajor != "" && latestForBaseMajor != r.base.version {
-		setNotValid(fmt.Sprintf("Can only suggest a release version when compared against the most recent version of this major: %s.", latestForBaseMajor))
+		setNotValid("Can only suggest a release version when compared against the most recent version of this major: %s.", latestForBaseMajor)
 		return
 	}