FINERACT-2567: Fix error messages in exception classes

[rhopman]

Several exception classes contain error messages and comments that are incorrect, misleading, or contain copy-paste mistakes. These messages are returned as part of API error responses and seen by API clients and end users.

Checklist

• Write the commit message as per our guidelines
• Acknowledge that we will not review PRs that are not passing the build ("green") - it is your responsibility to get a proposed PR to pass the build, not primarily the project's maintainers.
• Create/update unit or integration tests for verifying the changes made.
• Follow our coding conventions.
• Add required Swagger annotation and update API documentation at fineract-provider/src/main/resources/static/legacy-docs/apiLive.htm with details of any API changes
• This PR must not be a "code dump". Large changes can be made in a branch, with assistance. Ask for help on the developer mailing list.