deps: add example of comparing OpenSSL changes

When upgrading OpenSSL, Step 6 in upgrading guide explains the steps that need to be taken if asm files need updating. This might not always be the case and something that needs to be checked from release to release.

This commit adds an example of using github to manually compare two tags to see if any changes were made to asm files.

Checklist

• commit message follows commit guidelines

Affected core subsystem(s)

deps