typo in rules/xla/concat/Main.hs rule04

[junminjang]

I know it is not that important.. but I think it should be fixed

This PR adds the following changes/fixes/enhancements:

• fixed typo in line 59

...

Checks

• [v] Did you run ormolu, a Haskell Formatter? Run ormolu --mode inplace $(git ls-files '*.hs') to format all files in the project.
• [] Did you update hie.yaml using the command gen-hie > hie.yaml?
• [v] Do all tests pass using stack test?