Fix the Bech32 character mutation test.

The test occasionally fails because it attempts to be extremely specific when
pattern matching the error produced by decoding a mutated string.

Unfortunately, changing just a single character in a valid Bech32 string can
cause the decoder to produce many different types of error, depending on
the location of the mutation, and the nature of the mutation.

We can prevent spurious failures by changing the test to be less specific:
we can expect merely that the string is rejected with some error.

(This already gets us most of what we want, namely that mutating a
character cause the resultant string to be rejected.)

lib/bech32/test/Codec/Binary/Bech32Spec.hs

@@ -58,7 +58,6 @@ import Test.QuickCheck
     , elements
     , property
     , (.&&.)
-    , (.||.)
     , (===)
     , (==>)
     )
@@ -203,15 +202,7 @@ spec = do
                     corruptedString /= originalString ==>
                         (T.length corruptedString === T.length originalString)
                         .&&.
-                        (result `shouldBe` Left
-                            StringToDecodeMissingSeparatorChar)
-                        .||.
-                        (result `shouldBe` Left
-                            (StringToDecodeContainsInvalidChars []))
-                        .||.
-                        (result `shouldBe` Left
-                            (StringToDecodeContainsInvalidChars
-                                [CharPosition index]))
+                        (result `shouldSatisfy` isLeft)
 
         it "Decoding fails for an upper-case string with a lower-case \
            \character." $