docs: fix by proofreading

Co-authored-by: Abdul Malik Ikhsan <[email protected]>

Author: kenjis

user_guide_src/source/installation/index.rst

@@ -3,7 +3,7 @@ Installation
 ############
 
 CodeIgniter4 can be installed in a number of different ways: manually,
-using `Composer <https://getcomposer.org>`_
+or using `Composer <https://getcomposer.org>`_
 Which is right for you?
 
 - We recommend the Composer installation because it keeps CodeIgniter up to date easily.