rc: remove OS X specific ssh-add

OS X OpenSSH doesn't work with VerifyHostKeyDNS=yes, so it OpenSSH must
be installed from Homebrew or MacPorts which (at least Homebrew) don't
support the flag to add the key to keychain.

rc/bashrc

@@ -106,7 +106,6 @@ if [[ $UNAME = Darwin ]]; then
     alias ls="ls -Gp"
     alias ll="ls -alFHGp"
     alias l="ls -CFGp"
-    alias ssh-add="\ssh-add -D && \ssh-add -K"
 fi
 
 # Add an "alert" alias for long running commands.  Use like so:

rc/zshrc

@@ -295,7 +295,6 @@ if [[ $UNAME = Darwin ]]; then
     alias ls="ls -Gp"
     alias ll="ls -alFHGp"
     alias l="ls -CFGp"
-    alias ssh-add="\ssh-add -D && \ssh-add -K"
 fi
 
 # Add an "alert" alias for long running commands.  Use like so: