bug: Incorrect parsing of doc comments

[wetneb]

Did you check existing issues?

• I have read all the tree-sitter docs if it relates to using the parser
• I have searched the existing issues of tree-sitter-rust

Tree-Sitter CLI Version, if relevant (output of tree-sitter --version)

No response

Describe the bug

Similarly to #244, the parsing of doc comments (things that start with ///) is also incorrect.

Steps To Reproduce/Bad Parse Tree

Parse the example below, you get:

(source_file [0, 0] - [4, 0]
  (mod_item [0, 0] - [3, 1]
    name: (identifier [0, 4] - [0, 9])
    body: (declaration_list [0, 10] - [3, 1]
      (function_item [1, 4] - [1, 23]
        (visibility_modifier [1, 4] - [1, 7])
        name: (identifier [1, 11] - [1, 18])
        parameters: (parameters [1, 18] - [1, 20])
        body: (block [1, 21] - [1, 23]))
      (line_comment [2, 4] - [3, 0]
        outer: (outer_doc_comment_marker [2, 6] - [2, 7])
        doc: (doc_comment [2, 7] - [3, 0])))))

This should generate an error instead.

Expected Behavior/Parse Tree

The following example is accepted by the grammar, while it shouldn't

mod tests {
    pub fn execute() {}
    /// hello world
}

The following example fails to associate the doc comment to the function declaration:

mod tests {
    /// hello world
    pub fn execute() {}
}

Repro

Parse the examples above.