Cleans up UpdateProjectStatistics concern

What does this MR do?

Cleans up UpdateProjectStatistics module a bit by:

• Renaming attributes from project_statistics_name to project_statistiscs_name
• Makes constructor arguments to be the same as the instance variables.
• Cleaning up the comments in the module
• Reordering the methods

Also, removes unused module in Ci::Build

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content