[readme] Fix fish load_nvm function

README.md

@@ -564,7 +564,7 @@ function load_nvm --on-variable="PWD"
   if test -n "$nvmrc_path"
     set -l nvmrc_node_version (nvm version (cat $nvmrc_path))
     if test "$nvmrc_node_version" = "N/A"
-      nvm install $nvmrc_node_version
+      nvm install (cat $nvmrc_path)
     else if test nvmrc_node_version != node_version
       nvm use $nvmrc_node_version
     end