Ensure that Linux pages refer to `export` for environment variables

[allanrogerr]

Describe the bug
Some Linux documents, such as the below, refer to the usage of set instead of export.
set should be used in Windows documentation.
e.g. https://min.io/docs/minio/linux/operations/monitoring/minio-logging.html#publish-server-logs-to-http-webhook

To Reproduce
This demonstrates why set should not be used for environment variables in Linux

ubuntu@miniohq-allan-1:~$ set TEST="on"
ubuntu@miniohq-allan-1:~$ echo $TEST

versus

ubuntu@miniohq-allan-1:~$ export TEST="on"
ubuntu@miniohq-allan-1:~$ echo $TEST
on

Expected behavior
set should not be used for environment variables in Linux
e.g.
Windows documentation

set MINIO_LOGGER_WEBHOOK_ENABLE_<IDENTIFIER>="on"

Linux documentation

export MINIO_LOGGER_WEBHOOK_ENABLE_<IDENTIFIER>="on"

Screenshots
See example of a Linux document using set incorrectly.
https://min.io/docs/minio/linux/operations/monitoring/minio-logging.html#publish-server-logs-to-http-webhook

Desktop (please complete the following information):
n/a

Smartphone (please complete the following information):
n/a

Additional context
None