Fix metric name

[perkons]

Description

Prometheus metric naming best practices not followed for metric name "oracledb_tablespace_free"

Fixes #372

Type of change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Renamed the metric in toml file and I am using it in production.

Screenshots (if appropriate):

Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] New and existing unit tests pass locally with my changes