Document URL: [Doc] Remove RHEL7 references from Satellite Tuning Performance guide

https://access.redhat.com/documentation/en-us/red_hat_satellite/6.14/html-single/tuning_performance_of_red_hat_satellite/index

Section Number and Name:

4.2. Enabling Tuned Profiles
5.4.5. Configuring the QPID mgmt-pub-interval Parameter

Describe the issue: Since Satellite 6.11 onward its supported on RHEL8 OS, hence remove RHEL7 references from Satellite Tuning Performance guide.

Suggestions for improvement: Replace or remove the RHEL7 keyword

Red Hat Enterprise Linux 7 -> Red Hat Enterprise Linux 8

Additional information: Can be implemented on Satellite 6.12/6.13/6.14