'brew doctor' provides bad example command

If there are multiple dependencies missing, 'brew doctor' can suggest
that you run something like:

  brew install autoconf libyaml autoconf, libyaml

This commit improves that output.

Closes Homebrew/homebrew#10720.

Signed-off-by: Max Howell <max@methylblue.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/Library/Contributions/examples/brew-missing.rb b/Library/Contributions/examples/brew-missing.rb
index b3f287541..50fae12e4 100755
--- a/Library/Contributions/examples/brew-missing.rb
+++ b/Library/Contributions/examples/brew-missing.rb
@@ -29,7 +29,7 @@ def main
 
     unless missing_deps.empty?
       print "#{f.name}: " if formulae_to_check.size > 1
-      puts "#{missing_deps * ', '}"
+      puts "#{missing_deps * ' '}"
     end
   end
 end