🐛 [firestore-bigquery-export] Task size too large errors occuring even with EXCLUDE_OLD_DATA set to yes/true

### [READ] Step 1: Are you in the right place?

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### [REQUIRED] Step 2: Describe your configuration

- Extension name: **firestore-bigquery-export**
- Extension version: **0.1.50**
- Configuration values (redact info where appropriate):
- BigQuery Dataset location: us
- BigQuery Project ID: xxx
- Database ID: (default)
- Collection path: xxx
- Enable Wildcard Column field with Parent Firestore Document IDs (Optional): false
- Dataset ID: xxx
- Table ID: xxx
- BigQuery SQL table Time Partitioning option type (Optional): DAY
- BigQuery Time Partitioning column name (Optional): timestamp
- Firestore Document field name for BigQuery SQL Time Partitioning field option (Optional): Parameter not set
- BigQuery SQL Time Partitioning table schema field(column) type (Optional): omit
- BigQuery SQL table clustering (Optional): document_id
- Maximum number of synced documents per second (Optional): 100
- Backup Collection Name (Optional): Parameter not set
- Transform function URL (Optional): Parameter not set
- Use new query syntax for snapshots: no
- Exclude old data payloads (Optional): yes
- Use Collection Group query (Optional): no
- Cloud KMS key name (Optional): Parameter not set

### [REQUIRED] Step 3: Describe the problem

Even when using the `EXCLUDE_OLD_DATA` setting to prevent old_data from being populated, we are still seeing `Task size too large` errors on many messages. This might mean that firestore payloads close to 1MB are being padded in a way that the subsequent Task exceeds 1MB

#### Steps to reproduce:

1. Install extension version 0.1.50, ensure that `Exclude old data payloads` is set to `yes`
2. Write a large document to firestore

##### Expected result

No `Task size too large` errors should appear at all.

##### Actual result

Observing many `Task size too large` errors in logs.