perf: increase dashboard to 30d of history

For golang/go#48803.

Change-Id: I80a6ab9f07d274a3e133c01ba09b364ec9a57e08
Reviewed-on: https://go-review.googlesource.com/c/build/+/412392
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
diff --git a/perf/app/dashboard.go b/perf/app/dashboard.go
index 3e37317..c917a44 100644
--- a/perf/app/dashboard.go
+++ b/perf/app/dashboard.go
@@ -70,7 +70,7 @@
 	// data.
 	query := fmt.Sprintf(`
 from(bucket: "perf")
-  |> range(start: -7d)
+  |> range(start: -30d)
   |> filter(fn: (r) => r["_measurement"] == "benchmark-result")
   |> filter(fn: (r) => r["name"] == "%s")
   |> filter(fn: (r) => r["unit"] == "%s")