fix : Update the minimum required Linux kernel version

[Vperiodt]

fix for :- coroot/coroot#564

[def]

In reality, the agent works fine on most kernels starting from 4.16. For example, RHEL uses 4.18. The issue is that upstream kernels before 5.1 have a low limit on the number of eBPF instructions, but vendors often raise this limit in their builds. So we decided to list 5.1 as the minimum requirement but not enforce it strictly in the code.

[Vperiodt]

In reality, the agent works fine on most kernels starting from 4.16. For example, RHEL uses 4.18. The issue is that upstream kernels before 5.1 have a low limit on the number of eBPF instructions, but vendors often raise this limit in their builds. So we decided to list 5.1 as the minimum requirement but not enforce it strictly in the code.

oh! so should i keep the doc changes and revert the rest of it?