doc: use colon consistently in assert.md

PR-URL: #17463
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: Trott

doc/api/assert.md

@@ -381,13 +381,13 @@ assert.notDeepEqual(obj1, obj1);
 // AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }
 
 assert.notDeepEqual(obj1, obj2);
-// OK, obj1 and obj2 are not deeply equal
+// OK: obj1 and obj2 are not deeply equal
 
 assert.notDeepEqual(obj1, obj3);
 // AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }
 
 assert.notDeepEqual(obj1, obj4);
-// OK, obj1 and obj4 are not deeply equal
+// OK: obj1 and obj4 are not deeply equal
 ```
 
 If the values are deeply equal, an `AssertionError` is thrown with a `message`