audit: uniformize the desc problems

Closes Homebrew/homebrew#45492.

Signed-off-by: Baptiste Fontaine <batifon@yahoo.fr>

Library/Homebrew/cmd/audit.rb

@@ -390,7 +390,7 @@ class FormulaAuditor
     end
 
     if desc =~ /^([Aa]n?)\s/
-      problem "Please remove the indefinite article \"#{$1}\" from the beginning of the description"
+      problem "Description shouldn't start with an indefinite article (#{$1})"
     end
 
     if desc =~ /^#{formula.name} is\s/i