Update doctests for GHC 9.2.

New versions of GHC have become smarter about preserving type synonyms
in type signatures displayed to the user. In colonnade, there are several
instances where GHC used to report [Char], and it now reports String.
The doctests have been updated to pass on newer versions of GHC. They
will now fail on older versions of GHC though.

colonnade/src/Colonnade.hs

@@ -95,7 +95,7 @@ import qualified Data.Vector as Vector
 -- >>> let showDollar = (('$':) . show) :: Int -> String
 -- >>> colHouse = mconcat [headed "Color" (show . color), headed "Price" (showDollar . price)]
 -- >>> :t colHouse
--- colHouse :: Colonnade Headed House [Char]
+-- colHouse :: Colonnade Headed House String
 -- >>> let houses = [House Green 170000, House Blue 115000, House Green 150000]
 -- >>> putStr (ascii colHouse houses)
 -- +-------+---------+
@@ -179,10 +179,10 @@ fromMaybe c (E.Colonnade v) = E.Colonnade $ flip Vector.map v $
 -- >>> let allColors = [Red,Green,Blue]
 -- >>> let encColor = columns (\c1 c2 -> if c1 == c2 then "✓" else "") (Headed . show) allColors
 -- >>> :t encColor
--- encColor :: Colonnade Headed Color [Char]
+-- encColor :: Colonnade Headed Color String
 -- >>> let encHouse = headed "Price" (showDollar . price) <> lmap color encColor
 -- >>> :t encHouse
--- encHouse :: Colonnade Headed House [Char]
+-- encHouse :: Colonnade Headed House String
 -- >>> putStr (ascii encHouse houses)
 -- +---------+-----+-------+------+
 -- | Price   | Red | Green | Blue |
@@ -274,7 +274,7 @@ replaceWhen = modifyWhen . const
 --   
 --   >>> let cor = mconcat [cap "Person" colPersonFst, cap "House" colHouseSnd]
 --   >>> :t cor
---   cor :: Cornice Headed ('Cap 'Base) (Person, House) [Char]
+--   cor :: Cornice Headed ('Cap 'Base) (Person, House) String
 --   >>> putStr (asciiCapped cor personHomePairs)
 --   +-------------+-----------------+
 --   | Person      | House           |