[2.3] use caret to specify requirements

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Thanks to @javiereguiluz, I just learned about [caret versions for composer](https://getcomposer.org/doc/01-basic-usage.md#next-significant-release-tilde-and-caret-operators-)
Lets use them to make composer.json files simpler.