1.8.1.0 to 2.3.5 ignored table gives "not found" MySQL error

### Preconditions

1. Source: 1.8.1.0 community
2. Destination: 2.3.5 community
3. Local install using markshust docker setup (https://github.com/markshust/docker-magento)
4. Fresh install of m2
5. Ran migrate:settings
6. Ran migrate:data
7. Verified map.xml has ignored this table (prefix_yotpo_rich_snippets)

### Steps to reproduce
This happens on a fresh 2.3.5 install, it runs for quite a while first, and then fails on the map step following CustomerAttributes.

### Expected result
Map to proceed to next stage, as this table is ignored.

### Actual result
`[2020-05-30 21:58:46][INFO][mode: data][stage: integrity check][step: Url Rewrite Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: integrity check][step: Log Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: integrity check][step: Ratings Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: integrity check][step: ConfigurablePrices step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: integrity check][step: OrderGrids Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: integrity check][step: Tier Price Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: integrity check][step: SalesIncrement Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: integrity check][step: Inventory Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: setup triggers][step: Stage]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: data migration][step: EAV Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: volume check][step: EAV Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: data migration][step: Customer Attributes Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: volume check][step: Customer Attributes Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: data migration][step: Map Step]: started
[2020-05-30 21:58:46][INFO][mode: data][stage: volume check][step: Map Step]: started
100% [============================] Remaining Time: < 1 sec
In Mysql.php line 110:

SQLSTATE[42S02]: Base table or view not found: 1146 Table 'defaultdb.cabhubyotpo_rich_snippets' doesn't exist, query was: SELECT COUNT(*) FROM `cabhubyotpo_rich_snippets``

### Additional notes

Start with the Map Step reached by migrate:data after Customer Attributes Step, and inspect the ignored-table handling in map.xml. Trace the query reported at Mysql.php line 110 for the missing yotpo_rich_snippets table. Done means an ignored source table no longer causes the migration to fail and the Map Step proceeds.

Written by the indexing model from the issue text.