Tests.QuickCheckUtils: i Arbitrary Text: refactor

Decided to look into it because Text was using String generator. And that is a
strange beginning for Text.
Then String, better to depend on list as a classical lazy generator. And then
even list can be updated to other builder if needed.

There was rewrapping play on internal `arbitrary` types&functions.

This is the exactly same code, which got rewrapped manually, generation just classically
derives from 'arbitraryUnicodeChar :: Gen Char'.

Author: Anton-Latukha

tests/Tests/QuickCheckUtils.hs

@@ -85,7 +85,7 @@ instance Arbitrary a => Arbitrary (Sqrt a) where
     shrink = map Sqrt . shrink . unSqrt
 
 instance Arbitrary T.Text where
-    arbitrary = (T.pack . getUnicodeString) `fmap` arbitrary
+    arbitrary = T.pack <$> listOf arbitraryUnicodeChar -- without surrogates
     shrink = map T.pack . shrink . T.unpack
 
 instance Arbitrary TL.Text where