[Bug] Dockerfile READMEs refer to Snowflake instead of Redshift, BigQuery, and Spark

### Is this a new bug?

- [x] I believe this is a new bug
- [x] I have searched the existing issues, and I could not find an existing issue for this bug

### Which packages are affected?

- [ ] dbt-adapters
- [ ] dbt-tests-adapter
- [ ] dbt-athena
- [ ] dbt-athena-community
- [x] dbt-bigquery
- [ ] dbt-postgres
- [x] dbt-redshift
- [ ] dbt-snowflake
- [x] dbt-spark

### Current Behavior

### Correct

"Snowflake" is correct here:
https://github.com/dbt-labs/dbt-adapters/blob/05c094e536f1366b75b1c5315f0d314182b74ed7/dbt-snowflake/docker/README.md?plain=1#L27-L33

"Postgres" is correct here:

https://github.com/dbt-labs/dbt-adapters/blob/05c094e536f1366b75b1c5315f0d314182b74ed7/dbt-postgres/docker/README.md?plain=1#L27-L32

### Incorrect

"Snowflake" should be "BigQuery" here:
https://github.com/dbt-labs/dbt-adapters/blob/05c094e536f1366b75b1c5315f0d314182b74ed7/dbt-bigquery/docker/README.md?plain=1#L26-L33

"Snowflake" should be "Redshift" here:
https://github.com/dbt-labs/dbt-adapters/blob/05c094e536f1366b75b1c5315f0d314182b74ed7/dbt-redshift/docker/README.md?plain=1#L27-L33

"Snowflake" should be "Spark" here:
https://github.com/dbt-labs/dbt-adapters/blob/05c094e536f1366b75b1c5315f0d314182b74ed7/dbt-spark/docker/README.md?plain=1#L26-L32

### Expected Behavior

Correct names in the comments

### Steps To Reproduce

See above

### Relevant log output

```shell

```

### Environment

```markdown
- OS:
- Python:
- dbt-adapters:
- :
```

### Additional Context

_No response_