Remove autoWidth from Dropdown

[cagataycivici]

autoWidth causes significant performance problems so remove the property and let the page author define the width of the dropdown.

[dmytro-gokun]

@cagataycivici I think CHANGELOG has to be updated, so this is listed as a breaking change

[mertsincan]

@dmytro-gokun, Thanks a lot for your suggestion. Fixed now. Please check it ;)

https://github.com/primefaces/primeng/blob/master/CHANGELOG.md

[dmytro-gokun]

@mertsincan I hate too be that pedantic, but i'd expect to see that under 7.1.0, not 7.1.0-rc.1
You see, we use your great library in a stable product and we do not update to release candidates. So, the only time we update is when there is a new stable version out. And a changelog for that version is what we check to see if there any breaking changes that require our attention. And I think this is how the most of enterprise customers do it..