[CodeCompletion] Remove the last use of ReusePrecheckedType.
[CodeCompletion] Remove the last use of ReusePrecheckedType.

Now that operator code completion uses opaque placeholder exprs,
there's no need to pass the flag to use prechecked types in the
constraint system.

glessard/swift,benlangmuir/swift,benlangmuir/swift,benlangmuir/swift,JGiola/swift,JGiola/swift,roambotics/swift,JGiola/swift,glessard/swift,roambotics/swift,roambotics/swift,glessard/swift,roambotics/swift,JGiola/swift,roambotics/swift,glessard/swift,JGiola/swift,benlangmuir/swift,glessard/swift,JGiola/swift,apple/swift,apple/swift,benlangmuir/swift,roambotics/swift,apple/swift,apple/swift,benlangmuir/swift,glessard/swift,apple/swift,apple/swift