Apply suggestions from code review

Co-authored-by: Vitalii Elenhaupt <3624712+veelenga@users.noreply.github.com>

spec/ameba/rule/performance/minmax_after_map_spec.cr

@@ -4,7 +4,7 @@ module Ameba::Rule::Performance
   subject = MinMaxAfterMap.new
 
   describe MinMaxAfterMap do
-    it "passes if there is no potential performance improvements" do
+    it "passes if there are no potential performance improvements" do
       expect_no_issues subject, <<-CRYSTAL
         %w[Alice Bob].map { |name| name.size }.min(2)
         %w[Alice Bob].map { |name| name.size }.max(2)