v2.9.0

Features

• update protos from upstream (#1206) (33526b0)

Bug Fixes

• bind promisify calls for flush() so they have a 'this' value (#1184) (e494fb7)
• deps: update dependency google-auth-library to v7 (#1207) (fce2af1)
• openTelemetry doc fails to generate for #1185 (#1200) (0600bde)
• update synchronousPull example to avoid INVALID_ARGUMENT error (#1194) (1f85345)