Block Mover wording: 'Move block position' to 'Change block position'

[illusaen]

Description

Changing 'Move block position' to 'Change block position' for block mover as per Slack chat with Wordpress.org folks, cc: @hypest, @iamthomasbishop.

How has this been tested?

1. Insert paragraph block and type text.
2. Insert heading block.
3. Long press up block mover.
4. Confirm that title on popped up action sheet says 'Change block position'.

Screenshots

iOS	Android

Types of changes

Grammatical bug fix.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

[iamthomasbishop]

@illusaen Sounds good to me! 👍

[mchowning]

Looks good and works as expected. Thanks @illusaen ! 🙇