[TT-5936]Error log should be optional

[cuongpv1309]

Change error log to warning

Description

• in file mw_jwt.go, i create polErrors := "" to store policyID. Finally, i just log.warnf it.

Related Issue

#https://github.com/TykTechnologies/tyk/issues/4152

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Refactoring or add test (improvements in base code or adds test coverage to functionality)

[mguggi]

@linhhahoang1999 Are there any plans to fix this problem in upcoming releases?