website: Small corrections to the "plan" and "apply" command docs

The "apply" documentation contained a simple typo, while the "plan"
documentation contained outdated information about using
"terraform plan PLANFILE" to view a plan. The latter is now a separate
command entirely, since Terraform 0.12: "terraform show PLANFILE".

website/docs/commands/apply.html.markdown

@@ -18,7 +18,7 @@ Usage: `terraform apply [options] [dir-or-plan]`
 
 By default, `apply` scans the current directory for the configuration
 and applies the changes appropriately. However, a path to another configuration
-or an execution plan can be provided. Explicit execution plans files can be
+or an execution plan can be provided. Explicit execution plan files can be
 used to split plan and apply into separate steps within
 [automation systems](https://learn.hashicorp.com/terraform/development/running-terraform-in-automation).
 

website/docs/commands/plan.html.markdown

@@ -33,11 +33,6 @@ Usage: `terraform plan [options] [dir]`
 By default, `plan` requires no flags and looks in the current directory
 for the configuration and state file to refresh.
 
-If the command is given an existing saved plan as an argument, the
-command will output the contents of the saved plan. In this scenario,
-the `plan` command will not modify the given plan. This can be used to
-inspect a planfile.
-
 The command-line flags are all optional. The list of available flags are:
 
 * `-compact-warnings` - If Terraform produces any warnings that are not