And it's messing with tests!

In T396900#10914709, @mpopov wrote:

Test failed https://gitlab.wikimedia.org/repos/data-engineering/schemas-event-secondary/-/jobs/536479

1) Schema Compatibility in Repository ./jsonschema/
       analytics/product_metrics/web/translation
         Major Version 1
           1.4.2 must be compatible with 1.0.0:

      AssertionError [ERR_ASSERTION]: Error at path: .properties.element_id.mexLength
      + expected - actual

       {
         "description": "The ID of the UI element that was clicked."
      -  "maxLength": 64
      +  "mexLength": 64
         "type": "string"
       }

All schemas affected by typo: https://codesearch.wmcloud.org/analytics/?q=mexLength&files=&excludeFiles=&repos=repos%2Fdata-engineering%2Fschemas-event-secondary