missing-natspec-comments incorrectly emits missing title on functions

[cryppadotta]

In missing-natspec-comments functions are added to the list of nodes to be evaluated and it checks that they have a title.

However, according to the format specification @title applies only to contract and interface, not function.

In fact, adding a @title to a function natspec will result in solc reporting:

DocstringParsingError: Doc tag @title not valid for functions.

[come-maiz]

Nice catch @cryppadotta! Please review the linked pull request. The doc says that all the tags are optional, so I'm not sure if we should just completely remove the title requirement. What do you think? Do you find it useful?

pura vida