test: Make regex tests match diagnostics

Author: sgillespie

plugins/hls-change-type-signature-plugin/test/testdata/TRigidType.txt

@@ -1,11 +1,3 @@
-Expected: a -> [[Int]]
-  Actual: [[Int]] -> [[Int]]
-‘a’ is a rigid type variable bound by
-  the type signature for:
-    test :: forall a. a -> Int
-  at /home/sgillespie/dev/haskell/haskell-language-server/plugins/hls-change-type-signature-plugin/test/testdata/TRigidType.hs:3:1-16
-In the second argument of ‘(.)’, namely ‘reverse’
-In the second argument of ‘(.)’, namely ‘head . reverse’
 In the expression: go . head . reverse
 Relevant bindings include
   test :: a -> Int

plugins/hls-change-type-signature-plugin/test/testdata/TRigidType2.txt

@@ -1,10 +1,3 @@
-Couldn't match type ‘a’ with ‘[Int]’
-Expected: a -> Int
-  Actual: [Int] -> Int
-‘a’ is a rigid type variable bound by
-  the type signature for:
-    test :: forall a. a -> Int
-  at /home/sgillespie/dev/haskell/haskell-language-server/plugins/hls-change-type-signature-plugin/test/testdata/TRigidType2.hs:3:1-16
 In the expression: head
 In an equation for ‘test’: test = head
 Relevant bindings include