Ignore keyword order for keyword-based grammars

The order of the input list affected the final grammar, which is
unintuitive behavior. The keywords are now sorted to prevent unnecessary
differences between grammars.

In addition, I removed the documentation that `keywords` could be a list
of `DAIDEObject`s because the code itself does not support that.

src/daidepp/grammar/grammar_utils.py

@@ -226,8 +226,7 @@ def create_grammar_from_press_keywords(
     Parameters
     ----------
     keywords : List[PressKeywords]
-        List of press keywords. Although the type hint says List[PressKeywords],
-        this can be a list of string literals or DAIDEObjects (to avoid circular imports).
+        List of press keywords.
     allow_just_arrangement : bool, optional
         if set to True, the parser accepts strings that are only arrangements, in
         addition to press messages. So, for example, the parser could parse, by default False
@@ -247,6 +246,9 @@ def create_grammar_from_press_keywords(
     if allow_just_arrangement and string_type == "message":
         string_type = "arrangement"
 
+    # The input order or any duplicate elements should not affect the generated grammar
+    keywords = sorted(set(keywords))
+
     full_grammar = create_daide_grammar(
         level=MAX_DAIDE_LEVEL,
         string_type=string_type,