gh-37882: eclib: fix doctests after 20240408 update
With the update to 20240408 and later, the output of eclib has some
extra information that makes some doctests fail. This PR adds some `...`
in the right spots so the tests still pass after the update, without
affecting previous versions of eclib
### :memo: Checklist
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URL: https://github.com/sagemath/sage/pull/37882
Reported by: Gonzalo Tornaría
Reviewer(s): John Cremona
