[toplevel] Remove unusable option -notop

Maxime points out that -notop cannot be used as the kernel requires
all constants to belong into a module. Indeed:

```
$ rlwrap ./bin/coqtop -notop
Coq < Definition foo := True.
Toplevel input, characters 0-23:
> Definition foo := True.
> ^^^^^^^^^^^^^^^^^^^^^^^
Error: No session module started (use -top dir)
Coq < Module M. Definition foo := True. End M.
Module M is defined
Coq < Locate foo.
Constant If you see this, it's a bug.M.foo
  (shorter name to refer to it in current context is M.foo)
```

My rationale for the removal is that this kind of incomplete features
are often confusing to newcomers ─ it has happened to me many times ─
as it can be seen for example in #397 .

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/safe_typing.ml b/kernel/safe_typing.ml
index e4b3fcbf1..2312f891c 100644
--- a/kernel/safe_typing.ml
+++ b/kernel/safe_typing.ml
@@ -71,7 +71,7 @@ module NamedDecl = Context.Named.Declaration
   - [env] : the underlying environment (cf Environ)
   - [modpath] : the current module name
   - [modvariant] :
-    * NONE before coqtop initialization (or when -notop is used)
+    * NONE before coqtop initialization
     * LIBRARY at toplevel of a compilation or a regular coqtop session
     * STRUCT (params,oldsenv) : inside a local module, with
       module parameters [params] and earlier environment [oldsenv]