Update writing-tests.md

Extra `:` at the end of the line was breaking the markdown parser for table layout:

Fixes "Error in user YAML: (<unknown>): mapping values are not allowed in this context"

writing-tests.md

@@ -1,6 +1,6 @@
 ---
 title: Writing Tests
-description: Next let's get a brief overview of how to write tests using Pest. After successfully installing Pest, you will find the following files and folders in your project:
+description: Next let's get a brief overview of how to write tests using Pest. After successfully installing Pest, you will find the following files and folders in your project
 ---
 
 # Writing Tests