minor #15313 Fix link to Composer (sebpacz)

This PR was merged into the 4.4 branch.

Discussion
----------

Fix link to Composer

By the way, I added a small change in the "Before You Start" section.

<!--

If your pull request fixes a BUG, use the oldest maintained branch that contains
the bug (see https://symfony.com/releases for the list of maintained branches).

If your pull request documents a NEW FEATURE, use the same Symfony branch where
the feature was introduced (and `5.x` for features of unreleased versions).

-->

Commits
-------

e8b682c Fix link to Composer

Author: xabbuh

create_framework/introduction.rst

@@ -64,7 +64,7 @@ Reading about how to create a framework is not enough. You will have to follow
 along and actually type all the examples included in this tutorial. For that,
 you need a recent version of PHP (7.4 or later is good enough), a web server
 (like Apache, nginx or PHP's built-in web server), a good knowledge of PHP and
-an understanding of Object Oriented programming.
+an understanding of Object Oriented Programming.
 
 Ready to go? Read on!
 
@@ -113,5 +113,5 @@ In the :doc:`next chapter </create_framework/http_foundation>`, we are going to
 introduce the HttpFoundation Component and see what it brings us.
 
 .. _`Symfony`: https://symfony.com/
-.. _`Composer`: https//getcomposer.org/
+.. _`Composer`: https://getcomposer.org/
 .. _`download and install Composer`: https://getcomposer.org/download/