[associations helper] Use JLoader to load the router to make association links

[andrepereiradasilva]

Summary of Changes

The component router helper should be registered in the component association helper so when loading the helper it's already auto-loaded.
So we drop jimport and use JLoader::register

Testing Instructions

In multilanguage site, weblinks Associations work fine (business as usual).

Notes

This issue was discovered in the GsoC multilingual association sproject.

Note: a similiar PR was made for joomla-cms repository (joomla/joomla-cms#11321).

@infograf768 @alikon @jreys please test

[alikon]

i've tested successfully

[andrepereiradasilva]

a change exactly like this (joomla/joomla-cms#11321) was already merged in joomla cms repository...

[yvesh]

I have tested this item ✅ successfully on 46eb172

Works as expected

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[andrepereiradasilva]

thanks