Factor out string for i18n

[zepumph]

No description provided.

[pixelzoom]

@zepumph No one is assigned and there's no information here abpout what string should be factored out. Please provide a description.

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This issue was apparently created to associate with this TODO in NumberSuiteCommonPreferencesNode.ts:

    // TODO: factor out this string if we like this, https://github.com/phetsims/number-suite-common/issues/26
    const loadAllHtmlText = new RichText(
      'To display a second language, run the <a href="{{url}}">“all” version</a> of Number Play.', {

Please don't create GitHub issues with no description. It wastes people's time.

[pixelzoom]

Move to #28