Dataset is spatial definition finalized and implemented

## User Story

In order to sync with Geoplatform as simply as possible, data.gov wants the is_spatial field to match exactly what geoplatform recognizes as "spatial" data.

## Acceptance Criteria

[ACs should be clearly demoable/verifiable whenever possible. Try specifying them using [BDD](https://en.wikipedia.org/wiki/Behavior-driven_development#Behavioral_specifications).]

- [ ] GIVEN NSDI/Geoplatform has a definition of spatial data that they pull from data.gov \
WHEN a user reviews both data.gov and geoplatform \
THEN datasets exist and/or counts are the same (accounting for recent changes that geoplatform hasn't pulled yet).

## Background

Need to have completed previous tickets on this story and work with NSDI and geoplatform to confirm criteria.

## Security Considerations ([required](https://nvd.nist.gov/800-53/Rev4/control/CM-4))

[comment]: # "Our SSP says 'The Data.gov team ensures security implications are considered as part of the agile requirements refinement process by including a section in the issue template used as a basis for new work.' so please don't remove this section without care."
None

## Sketch

Should probably involve removing the metadata spatial check of if the metadata has a valid spatial field, and just utilize if the `theme` contains the keyword `geospatial`. Will need to confirm with NSDI.

Start by reviewing the previous tickets in this story and confirming the spatial-data definition with NSDI and Geoplatform. Inspect the current metadata spatial check and the proposed theme keyword behavior; done means data.gov and Geoplatform contain the same datasets or counts, allowing for recent unsynced changes.

Written by the indexing model from the issue text.