zsh-syntax-highlighting: remove non-Homebrew-specific caveats.

Formula/zsh-syntax-highlighting.rb

@@ -20,16 +20,10 @@ class ZshSyntaxHighlighting < Formula
   def caveats
     <<-EOS.undent
     To activate the syntax highlighting, add the following at the end of your .zshrc:
-
       source #{HOMEBREW_PREFIX}/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh
 
-    You will also need to force reload of your .zshrc:
-
-      source ~/.zshrc
-
-    Additionally, if you receive "highlighters directory not found" error message,
+    If you receive "highlighters directory not found" error message,
     you may need to add the following to your .zshenv:
-
       export ZSH_HIGHLIGHT_HIGHLIGHTERS_DIR=#{HOMEBREW_PREFIX}/share/zsh-syntax-highlighting/highlighters
     EOS
   end