fix(cmd/gno): correctly filter filetests in listNonTestFiles

[harry-hov]

s/HasPrefix/HasSuffix

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (07c6065) 55.73% compared to head (c48175d) 55.73%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1560   +/-   ##
=======================================
  Coverage   55.73%   55.73%           
=======================================
  Files         435      435           
  Lines       65933    65933           
=======================================
  Hits        36748    36748           
  Misses      26303    26303           
  Partials     2882     2882           

Flag	Coverage Δ
go-1.21.x	∅ <ø> (∅)
misc	∅ <ø> (∅)
misc-_test.genstd	∅ <ø> (∅)

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