[#911] fix sql cleaning

[matthewhilton]

Closes #911

Summary

It was clean_param being called when PARAM_TEXT that mangles the <= in the sql. I checked a similar plugin report_customsql, and it used PARAM_RAW

Testing

• Manually tested by putting in the SQL from the issue linked above into step definitions, saved, and confirmed no longer removes the text after the <=
• (side note, I attempted to add a unit test for this which appears possible https://moodledev.io/docs/4.5/apis/subsystems/form#unit-testing but I could not get it to work properly and it does not seem worth it to spend any longer)

** Cherry picks**

• [#911] fix sql cleaning #913

[Peterburnett]

LGTM. We need to allow carets, all other poweful syntax for SQL is already allowed in PARAM_TEXT eg ; ' "