As commented in MDL-38524 working with non-fixed behat dependencies can be complicated for maintenance reasons as there are different upstream project requiring different versions of different dependencies and changes can affect tests results. We can use wildcards (the latest version in composer nomenclature, 1.2.* for example) during DEV.

This change will be tied to changes in moodlehq/behatextension, we can begin with 1.26.* for 2.6 and switch the wildcards to fixed versions in 1.25.lastone for 2.5