schools: worker timeout on medium-sized school merge

[cyril-amar]

On URL https://prologin.org/schools/admin/merge/70896,70002?use=70896, submitting the form will raise a 405 Method Not Allowed error, after a while.

Workflow:

• search for two schools ENS Paris Saclay
• select them and try to merge them
• replace the default "Utiliser comme base" by the one with UAI = 0940607Z.
• submit the form

[lportemo]

This has been resolved by increasing the timeout on workers.