[Protostar] Equal field widths in mod_login

[ciar4n]

Pull Request for Issue #14010 .

Summary of Changes

Gives mod_login equal field widths (Display Labels: Icons).

Testing Instructions

Enable 'secret key' field and check front end login module.

Before PR

After PR

Documentation Changes Required

None

[ghost]

I have tested this item ✅ successfully on d269ac1

Thanks @ciar4n

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[alikon]

I have tested this item ✅ successfully on d269ac1

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/14027.}