document try step bugfix
concourse/concourse#4252
#### <sub><sup><a name="v550-note-9" href="#v550-note-9">:link:</a></sup></sub> fix
For the past few releases, the web nodes have allowed themselves to make up to 64 parallel connections to the database, to allow for parallelizing work like GC and scheduling within a single node. @ebilling has configured the web node's tolerance for idle connections to be more lenient: If a node has been using more than 32 of its available connections, up to 32 connections will be allowed to stay idly open. Anecdotally, CPU savings (resulting from less opening/closing of connections) of up to 30% have been observed on web nodes because of this change. Furthermore, the total max connection pool size has been made configurable - this should allow operators to avoid overloading the max connection limit on the database side #4232.
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+#### <sub><sup><a name="v550-note-10" href="#v550-note-10">:link:</a></sup></sub> fix
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+@josecv found and fixed a subtle bug where, if you had a [`try`](https://concourse-ci.org/try-step.html) step and you aborted while the hooked step was running, your whole web node would [crash](https://github.com/concourse/concourse/issues/3989)! Good catch #4252.
