RevisionStore::getQueryInfo currently triggers a deprecation warning when called with the "text" flag while SCHEMA_COMPAT_READ_OLD is not set. This was introduced to given an early warning about such code, before SCHEMA_COMPAT_WRITE_OLD gets removed (T183487).
However, that means that we have to fix all such code (T198341) before we can make SCHEMA_COMPAT_READ_NEW the default on CI (T198561), because otherwise tests would fail due to the deprecation warning. This in turn would prevent us from making use of extra slots in product (T198308), which would block SDC deployment (T194750).
So instead, we disable the warnings temporarily, but block T183487: MCR schema migration stage 3: drop support for legacy fields (wmf production) on re-enabling them (T200918), which we can do once T198341: Remove all references to the rev_text_id and ar_text_id fields is done.