Fix warning for -Werror build in Circle CI (#4727)

* Fix typo in hls-signature-help-plugin

* Remove unused import

Author: fendor

plugins/hls-signature-help-plugin/src/Ide/Plugin/SignatureHelp.hs

@@ -94,7 +94,7 @@ help when a space char is inserted, we probably have to use up-to-date results.
 
 {-
 Here is a brief description of the algorithm of finding relevant bits from HIE AST
-1. let 'hsAppNode' = the smallest 'HsApp' AST node which contains the cursor postion
+1. let 'hsAppNode' = the smallest 'HsApp' AST node which contains the cursor position
    See 'extractInfoFromSmallestContainingFunctionApplicationAst'
 2. let 'functionNode' = the left-most node of 'hsAppNode'
    See 'getLeftMostNode'

plugins/hls-signature-help-plugin/test/Main.hs

@@ -5,7 +5,6 @@ import           Control.Arrow                            ((>>>))
 import           Control.Exception                        (throw)
 import           Control.Lens                             ((^.))
 import           Data.Maybe                               (fromJust)
-import           Data.String.Interpolate                  (__i)
 import           Data.Text                                (Text)
 import qualified Data.Text                                as T
 import           Development.IDE.Plugin.Completions.Types (PosPrefixInfo (PosPrefixInfo))