create: strip 'v' prefix from version

To fix subsequent `brew audit` error:

  * line 8, col 3: Version v0.38.1 should not have a leading 'v'

Library/Homebrew/formula_creator.rb

@@ -165,7 +165,7 @@ module Homebrew
         <% unless  @head %>
           url "#{@url}"
         <% unless  @version.detected_from_url? %>
-          version "#{@version}"
+          version "#{@version.to_s.delete_prefix('v')}"
         <% end  %>
           sha256 "#{@sha256}"
         <% end  %>