Move declaration closer to first reference point

Author: MaggieKimani1

src/Microsoft.OpenApi.Tool/OpenApiService.cs

@@ -37,16 +37,14 @@ public static void ProcessOpenApiDocument(
             }
 
             var stream = GetStream(input);
-
-            OpenApiDocument document;
-
             var result = new OpenApiStreamReader(new OpenApiReaderSettings
             {
                 ReferenceResolution = resolveExternal ? ReferenceResolutionSetting.ResolveAllReferences : ReferenceResolutionSetting.ResolveLocalReferences,
                 RuleSet = ValidationRuleSet.GetDefaultRuleSet()
             }
             ).ReadAsync(stream).GetAwaiter().GetResult();
 
+            OpenApiDocument document;
             document = result.OpenApiDocument;
 
             // Check if filter options are provided, then execute