Avoid using metaobjects in exceptions, they may result in mop close-over

Removed attributes of type Moose::Meta::TypeConstraint, Moose::Meta::Role
& Moose::Meta::Class
An instance of Moose::Meta::TypeConstraint is expected, not 'Str'

I did type_constraint => 'Str' earlier, which is wrong because type_constraint
should be an actual type constraint of type Moose::Meta::TypeConstraint or its subclass
minor correction in POD format
No need of type or type_name for this exception

If anyone gets this exception, then the problem is in
the user's code & it needs to be fixed.