Add default values for notif_template_html and notif_template_text

[kuba-orlik]

Ref #6551

When setting up synapse I found the lack of default values for these fields confusing. I encountered #6551 and decided to add the fields to sample config. Is it where defaults are taken from? If not, please correct me

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
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• Code style is correct (run the linters)

[richvdh]

Thank you for the contribution, but:

• this doesn't seem related to "matrix.org/sytest" "guest user can set displaynames is flaky" "eg https://buildkite.com/matrix-dot-org/synapse/builds/7348#f0749e42-bda8-48f9-95fb-3f862aa7fca4 # Started: 2020-02-26 09:55:08.990 # Ended: 2020-02-26 09:55:10.021 # Got 7, expected "creeper" for Room displayname at tests/30rooms/13guestaccess.pl line 190. # 0.167456: Registered new user @anon-20200226_095239-167:localhost:8831 # 0.919001: User @7:localhost:8831 joined room # { room_id => "!QgjZoiPzZxNvhctfuI:localhost:8831" }  #6994?
• the sample config is auto-generated: you need to update the source if changing it
• There is a defined convention for the formatting, which this doesn't follow. please see the code-style doc.
• there should be no need to set these options; they are deprecated and were recently removed from the sample doc.
• the checklist in the PR template is meant to be followed.

all in all... I'm a bit confused by what you are trying to achieve here.

[kuba-orlik]

* this doesn't seem related to #6994?

Ow, that's right. I think I mis-clicked the issue number suggestion that GH tried to autocomplete. I meant issue #6551. I've updated the description. Sorry for the mess.

* there should be no need to set these options; they are deprecated and were recently removed from the sample doc.

I set out to create this PR when I was setting up Synapse and it threw an error because these options were not define, as mentioned in #6551

* the checklist in the PR template is meant to be followed.

I will follow up on them as soon as I free some time to work on that further. I hope that I cleared up my intentions with this PR here :)

[deepbluev7]

I set out to create this PR when I was setting up Synapse and it threw an error because these options were not define, as mentioned in #6551

Please verify, if that still happens in 1.12.0. As far as I'm aware, this isn't an issue anymore.

[richvdh]

yeah I think this is misguided. closing for now at least.