[ConstraintSystem] Fix spacing issues with printing attributes.

[amritpan]

Type variables with only a literal kind attribute and no other attributes may print with incorrect spacing and [] styling, like so:

$T2 [allows bindings to: noescape] ] [with possible bindings: (subtypes of) String]
$T7 [allows bindings to: noescape] , [literal: interpolated string]] [with possible bindings: (subtypes of) Any]

Corrected, the attributes will print:

$T2 [allows bindings to: noescape] [with possible bindings: (subtypes of) String]
$T7 [allows bindings to: noescape] [attributes: [literal: interpolated string]] [with possible bindings: (subtypes of) Any]

This is an edit to #60205

[xedin]

@swift-ci please smoke test