docs: Removed misleading text

[breautek]

"This API is based on the W3C Geolocation API Specification, and only executes on devices that don't already provide an implementation."

is misleading because it sounds like you do not need the plugin if the browser has geolocation support,
however, the plugin still handles permissions regardless if it provides
a geolocation implementation or not.

Closes #186

Platforms affected

Motivation and Context

Description

Testing

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary