chore: make unused block hashes in testing header creation explicit

[tungleanh0902]

Description

closes: #3960

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against the correct branch (see CONTRIBUTING.md).
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards and Go style guide.
• Wrote unit and integration tests.
• Updated relevant documentation (docs/) or specification (x/<module>/spec/).
• Added relevant godoc comments.
• Provide a commit message to be used for the changelog entry in the PR description for review.
• Re-reviewed Files changed in the Github PR explorer.
• Review Codecov Report in the comment section below once CI passes.

[tungleanh0902]

@nghuyenthevinh2000

[tungleanh0902]

@colin-axner

[nghuyenthevinh2000]

Hi @crodriguezvega @colin-axner,

I hope that the IBC team will support some of our engineer contributions to ibc-go by approving workflows running. @tungle-notional is new to Cosmos, and he wants to put his engineering skill to test by learning to contribute to IBC - go. I will ensure that his contributions conform to conventional commits guidelines.

If this issue is irrelevent, we will look at other ones.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1c0c756) 81.59% compared to head (7d44576) 81.59%.
Report is 35 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##             main    #5857     +/-   ##
=========================================
  Coverage   81.59%   81.59%             
=========================================
  Files         199      198      -1     
  Lines       15167    12103   -3064     
=========================================
- Hits        12375     9876   -2499     
+ Misses       2326     1765    -561     
+ Partials      466      462      -4     

see 172 files with indirect coverage changes

[crodriguezvega]

Thank you, @tungle-notional! Welcome to Cosmos and looking forward to more contributions from you!

[DimitrisJim]

Thank you @nghuyenthevinh2000 and welcome @tungle-notional!

One point of feedback I'd give back is to always make sure you first request to work on a feature by dropping a comment in the issue stating so. This is the easiest way to make sure work is not duplicated and does not go in vain and helps smooth out the contribution process. We have a contributing document https://github.com/cosmos/ibc-go/blob/main/CONTRIBUTING.md to get everyone up to speed.

Thanks again for opening the PR and welcome aboard! ❤️

[DimitrisJim]

made this private! its used inside the testing package so we needn't expose it for the time being!

[DimitrisJim]

lgtm 🚀 thanks again!