period fix (#87)

https://docs-mongodbcom-staging.corp.mongodb.com/kotlin/docsworker-xlarge/master/fundamentals/builders/#:~:text=instead%20of%20compile%20time.

Author: rustagir

source/fundamentals/builders.txt

@@ -46,7 +46,7 @@ Using the builders class, you leverage the power of:
 When using builders, the Kotlin compiler and the IDE catch errors such as misspelled
 operators early on. When using the MongoDB shell or plain Kotlin, you
 write operators as strings and get no visual indication of a problem,
-pushing these errors to runtime instead of compile time
+pushing these errors to runtime instead of compile time.
 
 With the builder classes, you write operators as methods. The IDE
 instantly underlines and gives you a red bar on the right indicating