fix(flex-setup): signature verification failed

[manojs1978]

Describe the bug
signature verification failed

To Reproduce
Steps to reproduce the behavior:

1. add required repos
2. follow steps in https://docs.gluu.org/v5.1.4.nightly/install/vm-install/suse/
3. download and install flex
4. verify rpm file as per given instruction
5. See error

Expected behavior
should not get signatre verification

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: suse
• Browser [e.g. chrome, safari]
• Version 15sp5
  -flex 5.1.4.nightly
  -DB opendj
  Smartphone (please complete the following information):
• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.