BLD: pin extension-helpers to 1.* following upstream recommendation

[neutrinoceros]

following https://github.com/astropy/extension-helpers/pull/72

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (783f217) 93.09% compared to head (a37c370) 83.75%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #80 +/- ## ========================================== - Coverage 93.09% 83.75% -9.35% ========================================== Files 7 6 -1 Lines 782 437 -345 Branches 12 0 -12 ========================================== - Hits 728 366 -362 - Misses 54 71 +17 ```

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[neutrinoceros]

I don't think CI errors are related; In any case, please let me know if you need a hand with it, I'd be happy to help !

[neutrinoceros]

ping @hamogu

[saimn]

Thanks