src/assets/i18n: update English strings

[alanorth]

Description

Re-word two messages for better English and consistency with other similar strings.

For example, on the homepage we say "Communities in DSpace":

... but on the sub-community pages we say "Communities of community name" and "Collections of community name":

It sounds more natural in English to say "in", and is more consistent with the language on the homepage.

Instructions for Reviewers

Build and run the application to see if the new strings appear on sub-community pages.

List of changes in this PR:

• Update two English strings

Include guidance for how to test or review your PR. This may include: steps to reproduce a bug, screenshots or description of a new feature, or reasons behind specific changes.

Checklist

This checklist provides a reminder of what we are going to look for when reviewing your PR. You need not complete this checklist prior to creating your PR (draft PRs are always welcome). If you are unsure about an item in the checklist, don't hesitate to ask. We're here to help!

• My PR is small in size (e.g. less than 1,000 lines of code, not including comments & specs/tests), or I have provided reasons as to why that's not possible.
• My PR passes ESLint validation using yarn lint
• My PR doesn't introduce circular dependencies (verified via yarn check-circ-deps)
• My PR includes TypeDoc comments for all new (or modified) public methods and classes. It also includes TypeDoc for large or complex private methods.
• My PR passes all specs/tests and includes new/updated specs or tests based on the Code Testing Guide.
• If my PR includes new libraries/dependencies (in package.json), I've made sure their licenses align with the DSpace BSD License based on the Licensing of Contributions documentation.
• If my PR includes new features or configurations, I've provided basic technical documentation in the PR itself.
• If my PR fixes an issue ticket, I've linked them together.

[tdonohue]

👍 Thanks @alanorth . This looks good to me, and I agree it makes sense.