fix: fix pipeline failure due to bigquery Provided Schema does not match Table.

[zhumin8]

fix kokoro job failing with error message:

+ bq load --autodetect --project_id=cloud-java-metrics --source_format=CSV client_library_versions.cloud_java_client_library_release_dates cloud_java_client_library_release_dates.csv
Upload complete.Waiting on bqjob_r28424c53fa9642fd_0000018b47445529_1 ... (0s) Current status: RUNNING                                                                                      Waiting on bqjob_r28424c53fa9642fd_0000018b47445529_1 ... (0s) Current status: DONE  

BigQuery error in load operation: Error processing job
'cloud-java-metrics:bqjob_r28424c53fa9642fd_0000018b47445529_1': Provided Schema
does not match Table cloud-java-metrics:client_library_versions.cloud_java_clien
t_library_release_dates. Cannot add fields (field: string_field_0)
Failure details:
- It looks like you are appending to an existing table with
autodetect enabled. Disabling autodetect may resolve this.

Relevant gcloud documentation: bq load

• remove --autodetect and use default false so destination table schema is used.
• --skip_leading_rows=1 since no need to infer schema as above.
• add --null_marker="-" to deal with empty release dates from source, e.g. for google-cloud-accessapproval:1.0.10

Manual script run and successfully run script to upload data.