remove trailing whitespace (#533)

With this commit, the below command produces no output when run in the
repo's root directory:

    git grep -r '[[:blank:]]$'

The commits that added the whitespace:
- a71637f lint: add annotation for key features in config.json
- fea7bcc lint: allow overlap of `files.example` and `files.exemplar` values
- d0cd08c lint: error on missing concept/exercise files
- 3a55f57 lint: support error annotations

In the future, we'll probably add whitespace-checking to CI.

src/lint/track_config.nim

@@ -198,7 +198,7 @@ proc isValidKeyFeature(data: JsonNode; context: string; path: Path): bool =
 
     For more information on key features see:
     https://exercism.org/docs/building/tracks/config-json#h-key-features""".unindent()
- 
+
   if isObject(data, context, path):
     let checks = [
       hasString(data, "icon", path, context, allowed = keyFeatureIcons,
@@ -717,7 +717,7 @@ proc checkFilePatternsOverlap(filePatterns: FilePatterns; trackSlug: string,
     ("test", "exemplar"),
     ("test", "editor"),
     ("editor", "example"),
-    ("editor", "exemplar"),    
+    ("editor", "exemplar"),
   ]
 
   var seenFilePatterns = initTable[string, HashSet[string]](250)
@@ -790,7 +790,7 @@ proc checkExerciseDirsAndTrackConfigAreInSync(trackDir: Path; data: JsonNode;
   ## Sets `b` to `false` if there is an exercise directory that is
   ## not an exercise `slug` in `data` and vice versa.
   for exerciseKind in ["concept", "practice"]:
-    let exerciseSlugs = getExerciseSlugs(data, exerciseKind)    
+    let exerciseSlugs = getExerciseSlugs(data, exerciseKind)
     let exercisesDir = trackDir / "exercises" / exerciseKind
     var exerciseDirSlugs = initHashSet[string]()
 

src/lint/validators.nim

@@ -419,7 +419,7 @@ proc hasArrayOfFiles*(data: JsonNode;
                       key: string;
                       path: Path;
                       context = "";
-                      relativeToPath: Path;                      
+                      relativeToPath: Path;
                       errorAnnotation = ""): bool =
   if hasArrayOfStrings(data, key, path, context):
     result = true