Change example in doc/bordeaux/elliptic_curves.rst

[cremona]

In William Stein's Bordeaux lectures he gave an example of an elliptic curve *not in the tables* (of conductor 154907). But as of version 4.8 that curve is in the tables in the optional larger database, and so that example causes a doctest failure in sage/doc/en/bordeaux/elliptic_curves.rst.

The patch changes the example to one whose conductor is larger.

To test: apply the patch and test sage/doc/en/bordeaux/elliptic_curves.rst both before and after installing the optional package at #11587 (i.e. ​http://wstein.org/home/ohanar/cremona-database/database_cremona_ellcurve-20111029.spkg).

[cremona]

Apply to 4.8 (e.g. 4.8.alpha4)

[jen]

This is a near-duplicate of #12617, so we should close this ticket in favor of that one.

[ohanar]

sounds good