[FIX] contributing: remove smart quotes

There have been several new odooers who've hit legal/cla mismatches, and after
investigation their email address would be smart quoted in git (e.g.
`<“uid@example.org”>`).

That the documentation itself uses smart quotes is highly suspicious, it would
make sense that new developers just pasted the provided command, updated it to
match, and didn't even notice the quotes were wrong: `git` is perfectly happy
with it, only on reading it back can you realise it's wrong and the guide
doesn't say anything about *that*.

So fix the quotes in the doc, and hopefully that'll resolve the issue.

closes odoo/documentation#10440

Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>

content/contributing/configure_git_authorship.rst

@@ -3,5 +3,5 @@ address you used to register on GitHub.
 
 .. code-block:: console
 
-   $ git config --global user.name “Your Name”
-   $ git config --global user.email “youremail@example.com”
+   $ git config --global user.name "Your Name"
+   $ git config --global user.email "youremail@example.com"