Fixed: Cleaning the French preposition 'à' from names

(cherry picked from commit 22005dc8c500cd77e4a710248582cd4a0036988f)

Closes #5213

src/NzbDrone.Core.Test/ParserTests/NormalizeTitleFixture.cs

@@ -24,6 +24,8 @@ namespace NzbDrone.Core.Test.ParserTests
         [TestCase("test/test", "testtest")]
         [TestCase("90210", "90210")]
         [TestCase("24", "24")]
+        [TestCase("Test: Something à Deux", "testsomethingdeux")]
+        [TestCase("Parler à", "parlera")]
         public void should_remove_special_characters_and_casing(string dirty, string clean)
         {
             var result = dirty.CleanArtistName();

src/NzbDrone.Core/Parser/Parser.cs

@@ -154,7 +154,7 @@ namespace NzbDrone.Core.Parser
                 new Regex(@"^b00bs$", RegexOptions.Compiled | RegexOptions.IgnoreCase)
             };
 
-        private static readonly RegexReplace NormalizeRegex = new RegexReplace(@"((?:\b|_)(?<!^)(a(?!$)|an|the|and|or|of)(?!$)(?:\b|_))|\W|_",
+        private static readonly RegexReplace NormalizeRegex = new RegexReplace(@"((?:\b|_)(?<!^)([aà](?!$)|an|the|and|or|of)(?!$)(?:\b|_))|\W|_",
                                                                 string.Empty,
                                                                 RegexOptions.IgnoreCase | RegexOptions.Compiled);
 
@@ -521,7 +521,7 @@ namespace NzbDrone.Core.Parser
 
             name = PercentRegex.Replace(name, "percent");
 
-            return NormalizeRegex.Replace(name).ToLower().RemoveAccent();
+            return NormalizeRegex.Replace(name).ToLowerInvariant().RemoveAccent();
         }
 
         public static string NormalizeTrackTitle(this string title)