fix: typos in documentation files

[maximevtush]

Description

Fixed typo in documentation files:

• spec/app/ics-020-fungible-token-transfer/README.md
• spec/core/ics-003-connection-semantics/README.md

Changed "propogating" to "propagating" and fixed some formatting in the documentation.

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Author Checklist

I have...

• included the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change (not needed for docs changes)
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• reviewed "Files changed" and left comments if necessary
• included the necessary unit and integration tests (not needed for docs changes)
• updated the relevant documentation or specification
• confirmed all CI checks have passed

[maximevtush]

@AdityaSripal @angbrav Hi! Just wanted to remind you about this PR. If you have some time, please take a look. Thank you!

[gjermundgaraba]

Hi, thank you for the PR, but we generally don't accept small non-functional changes (such as small text changes) without an accepted issue. This is because we get a lot of PRs and it takes up valuable time of the team without much value added.