🐛 [firestore-bigquery-export] Fix eventArc event types

[cabljac]

[REQUIRED] Step 3: Describe the problem

BQ export extension has firestore counter docs. Changing this in a new version will break any existing apps which rely on it though.

[Gustolandia]

@cabljac Can you please provide more details?

[Gustolandia]

#2244

addresses this.