Everywhere: Use ReadonlySpan<T> instead of Span<T const>

Author: https://github.com/MacDue
Commit: 63b11030f0
Pull-request: https://github.com/SerenityOS/serenity/pull/17328
Reviewed-by: https://github.com/trflynn89

Userland/Libraries/LibCore/ArgsParser.h

@@ -112,7 +112,7 @@ public:
     void add_positional_argument(Vector<StringView>& value, char const* help_string, char const* name, Required required = Required::Yes);
 
 private:
-    void autocomplete(FILE*, StringView program_name, Span<char const* const> remaining_arguments);
+    void autocomplete(FILE*, StringView program_name, ReadonlySpan<char const*> remaining_arguments);
 
     Vector<Option> m_options;
     Vector<Arg> m_positional_args;