[Docs] How to upgrade to a new version of the Academy Theme

[leecalcote]

Current State

This doc is missing upgrade instructions - https://docs.layer5.io/cloud/academy/creating-your-learning-path/

Desired State:

1. A new section that has make theme-upgrade included is needed.
2. Among other instructions, include this example:

$ make theme-upgrade
hugo mod get -u
hugo: collected modules in 1707 msgo: downloading github.com/layer5io/academy-theme v0.1.6
go: upgraded github.com/layer5io/academy-theme v0.1.5 => v0.1.6
go: upgraded github.com/twbs/bootstrap v5.3.6+incompatible => v5.3.7+incompatible

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