Keep escaped table name while migrating

[Glandos]

Q	A
Bug fix?	yes
New feature?	o
BC breaks?	no
Deprecations?	no
Tests pass?	yes/no
Documentation	no
Translation	no
CHANGELOG.md	no
License	MIT

Fix #6709

I don't now if this change will fit with MySQL.

[nicosomb]

Hello @Glandos. Thank you for your pull request.
Is that necessary to update all the database migrations files?

[Glandos]

Hmm, I don't know, since I was just upgrading from 2.5.x to 2.6.1, only this one was applied.
But my best guess is that yes, it's better to escape table name everywhere. However, testing for this is … tedious.

[j0k3r]

Good job.
I'm in the process of adding build to the CI so that we are actually testing wallabag when no database table prefix are defined.