Fix issue with missing package in go.sum

In another machine, this error appeared:

```
go: go.skia.org/infra@v0.0.0-20220714212951-8117921d36db requires
	cloud.google.com/go/bigtable@v1.6.0: missing go.sum entry; to add it:
	go mod download cloud.google.com/go/bigtable
```

Change-Id: Ie4fbcf83ad6eaff9fcdc033b8d1429b90fd81e1b
diff --git a/go.sum b/go.sum
index 65c4d88..6728582 100644
--- a/go.sum
+++ b/go.sum
@@ -34,6 +34,7 @@
 cloud.google.com/go/bigquery v1.5.0/go.mod h1:snEHRnqQbz117VIFhE8bmtwIDY80NLUZUMb4Nv6dBIg=
 cloud.google.com/go/bigquery v1.7.0/go.mod h1://okPTzCYNXSlb24MZs83e2Do+h+VXtc4gLoIoXIAPc=
 cloud.google.com/go/bigquery v1.8.0/go.mod h1:J5hqkt3O0uAFnINi6JXValWIb1v0goeZM77hZzJN/fQ=
+cloud.google.com/go/bigtable v1.6.0 h1:hcHWHVX8sfXW4qgfB0fYVd3i22Od2TK6gxoN7EWsbwY=
 cloud.google.com/go/compute v0.1.0/go.mod h1:GAesmwr110a34z04OlxYkATPBEfVhkymfTBXtfbBFow=
 cloud.google.com/go/compute v1.3.0/go.mod h1:cCZiE1NHEtai4wiufUhW8I8S1JKkAnhnQJWM7YD99wM=
 cloud.google.com/go/compute v1.5.0/go.mod h1:9SMHyhJlzhlkJqrPAc839t2BZFTSk6Jdj6mkzQJeu0M=