benchseries: remove unnecessary symbol in comment

Change-Id: Ide7abe4a8258d3649d6ea91de571033b20f8eff8
Reviewed-on: https://go-review.googlesource.com/c/perf/+/611136
Run-TryBot: shuang cui <imcusg@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Tim King <taking@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>

benchseries/benchseries.go

@@ -191,7 +191,7 @@ var noPuncDate = regexp.MustCompile("^[0-9]{8}T[0-9]{6}$")
 
 // RFC3339NanoNoZ has the property that formatted date&time.000000000 < date&time.000000001,
 // unlike RFC3339Nano where date&timeZ > date&timeZ.000000001Z
-// i.e., "Z" > "."" but "+" < "." so if ".000000000" is elided must use "+00:00"
+// i.e., "Z" > "." but "+" < "." so if ".000000000" is elided must use "+00:00"
 // to express the Z time zone to get the sort right.
 const RFC3339NanoNoZ = "2006-01-02T15:04:05.999999999-07:00"