Update use of Services in 3.5 dev docs

[kaitlinnewson]

Related issue: pkp/pkp-lib#9913

For the 3.5 developer documentation, use of Services needs to be updated in code examples, e.g.:

• https://docs.pkp.sfu.ca/dev/documentation/en/utilities-files
• https://docs.pkp.sfu.ca/dev/documentation/en/submission-files
• https://docs.pkp.sfu.ca/dev/documentation/en/statistics
• https://docs.pkp.sfu.ca/dev/documentation/en/statistics-editorial

Additionally, it would be good to check other changes in the 3.5 release notebook that may need updates in the dev docs.