Point the existing nil/NilClass pending spec at its tracking issue

This pending case already existed on master with a vague
"side of effect of inference changes" reason. It's the same
nil-doesn't-simplify-to-NilClass gap that's already tracked and
fixed (pending merge) in castwide#1223 and
#40. Make that traceable instead of leaving the
next reader to rediscover it.

Author: apiology

spec/complex_type/conforms_to_spec.rb

@@ -81,7 +81,13 @@ class Sub < Sup; end
   end
 
   it 'handles singleton types compared against their literals' do
-    pending 'side of effect of inference changes'
+    # https://github.com/castwide/solargraph/issues/1196
+    #
+    # `nil` doesn't yet simplify to `NilClass` the way other literals
+    # simplify to their class name. Fixed by
+    # https://github.com/castwide/solargraph/pull/1223 (stacked:
+    # https://github.com/apiology/solargraph/pull/40).
+    pending 'nil does not yet simplify to NilClass (issue #1196, fixed by PR #1223)'
     exp = Solargraph::ComplexType::UniqueType.new('nil', rooted: true)
     inf = Solargraph::ComplexType::UniqueType.new('NilClass', rooted: true)
     match = inf.conforms_to?(api_map, exp, :method_call)