[CS] Remove outdated assertion

We used to apply builder transforms to regular
functions without using a constraint system,
which is what the assertion is primarily geared
towards. However we now use a constraint system
for such cases, with the lack of a constraint
system only being used to check if we can even
apply the transform in the first place.

Author: hamishknight

lib/Sema/BuilderTransform.cpp

@@ -208,9 +208,6 @@ class BuilderClosureVisitor
                         DeclContext *dc, Type builderType,
                         Type bodyResultType)
       : cs(cs), dc(dc), ctx(ctx), builderType(builderType) {
-    assert((cs || !builderType->hasTypeVariable()) &&
-           "cannot handle builder type with type variables without "
-           "constraint system");
     builder = builderType->getAnyNominal();
     applied.builderType = builderType;
     applied.bodyResultType = bodyResultType;