Update docs/cases/cases-manage.asciidoc

Co-authored-by: Benjamin Ironside Goldstein <[email protected]>

Author: nastasha-solomon

docs/cases/cases-manage.asciidoc

@@ -220,7 +220,7 @@ NOTE: Each case can have a maximum of 50 observables.
 
 . Click *Add observable* to add the observable to the case. 
 
-After adding an observables to a case, you can remove or edit it by using the **Actions** menu (**…**).
+After adding an observable to a case, you can remove or edit it by using the **Actions** menu (**…**).
 
 TIP: Go to the **Similar cases** tab to access other cases with the same observables.