Simplify a few unsets

modules/editor/init.zsh

@@ -231,6 +231,5 @@ else
   print "omz: invalid keymap: $keymap" >&2
 fi
 
-unset keymap
+unset key{map,}
-unset key
 

modules/history-substring-search/init.zsh

@@ -13,8 +13,7 @@ if zstyle -t ':omz:module:history-substring-search' case-sensitive; then
 fi
 
 if ! zstyle -t ':omz:module:history-substring-search' color; then
-  unset HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND
+  unset HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_{FOUND,NOT_FOUND}
-  unset HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND
 fi
 
 bindkey -M emacs "$keyinfo[Control]P" history-substring-search-up

modules/spectrum/init.zsh

@@ -61,5 +61,5 @@ for color in {0..255}; do
   FG[$color]="\e[38;5;${color}m"
   BG[$color]="\e[48;5;${color}m"
 done
-unset colors color index
+unset color{s,} index
 

modules/ssh-agent/init.zsh

@@ -63,6 +63,5 @@ fi
 
 # Tidy up after ourselves.
 unfunction _ssh-agent-start
-unset _ssh_agent_forwarding
+unset _ssh_agent_{env,forwarding}
-unset _ssh_agent_env