IMAGEDAM-1096: update people field mapping to be case insensitive

[abdelrahmansd]

What does this change?

update elastic search Mapping (people field mapping) to be case insensitive

## How should a reviewer test this change? clean and set-up the grid locally to create the new mapping upload an image and add people to the image: **_`John Doe`_** and search for **_`john doe`_** using +person search filter should return that image

How can success be measured?

Who should look at this?

Tested? Documented?

• [x] locally by committer
• [ ] locally by Guardian reviewer
• [ ] on the Guardian's TEST environment
• [ ] relevant documentation added or amended (if needed)

[twrichards]

@paperboyo tested in our TEST environment and looks good - thank you @abdelrahmansd

[prout-bot]

Seen on auth, usage, image-loader, thrall, collections, media-api, kahuna (created by @abdelrahmansd and merged by @twrichards 12 minutes ago) Please check your changes!

[prout-bot]

Seen on metadata-editor, cropper (created by @abdelrahmansd and merged by @twrichards 12 minutes and 11 seconds ago) Please check your changes!

[prout-bot]

Seen on leases (created by @abdelrahmansd and merged by @twrichards 12 minutes and 23 seconds ago) Please check your changes!