Fix typo (#240)
Fix typo (#240)

`simultaenously` to `simultaneously`

Co-authored-by: Punya Biswal <a6e82da80f605f2d9fce3cce03422407d02a4b43@google.com>
census-ecosystem/opencensus-go-exporter-stackdriver,census-ecosystem/opencensus-go-exporter-stackdriver