fix(scraper.py): double sending articles

[Giuseppe-Tornello]

I figured out that the function soup.find_all('article') in line 178, listed two times some articles, here is the output of that function.
I currently have no clue about the reason of this behavior.

I found that <header class="sow-entry-header"> was exclusively used for articles, here is the output of soup.find_all('header', class_='sow-entry-header')
I tested this with the latest 10 ERSU articles and it works perfectly.

closes #40

[Helias]

merging this PR the bot will be updated, let's monitor for 1 month the ersu website and the channel to be sure that it continues to publish the articles

[Helias]

btw, good job!

[Giuseppe-Tornello]

Thank you!

[Giuseppe-Tornello]

I figured out that the function soup.find_all('article') in line 178, listed two times some articles, here is the output of that function.

I might have found a reason of that behavior.
By looking up the ERSU website i noticed this article structure:

<article ...>
  News
<article ...>
  Article1
</article>
<article ...>
  Article2
</article>
</article>

Since the function was looking for <article ...> </article> it led to return a duplicated value:
first of all it returned the content of the first <article> found, which in this case was the whole list of articles and then it returned the single articles.
I assume that a simpler way to fix this was to write something like this:
temp = soup.find('article')
articles = temp.find_all('article)

[Helias]

I am afraid that I could have done the mistake, due to the non-intuitive HTML structure.

Btw, if the current solution works we can keep as it is, otherwise feel free to open a new PR