Rename RETREIVAL_SIGNALS.md to RETRIEVAL_SIGNALS.md

Author: RaphaelFakhri

RETREIVAL_SIGNALS.md renamed to RETRIEVAL_SIGNALS.md

@@ -48,4 +48,4 @@ Twitter uses these user signals as training labels and/or ML features in the eac
 | Tweet Report          | Features           | N/A                | N/A                | N/A                | N/A                | N/A                |
 | Notification Open     | Features           | Features           | Features           | N/A                | Features           | N/A                |                       
 | Ntab click            | Features           | Features           | Features           | N/A                | Features           | N/A                |
-| User AddressBook      | N/A                | N/A                | N/A                | N/A                | Features           | N/A                |
+| User AddressBook      | N/A                | N/A                | N/A                | N/A                | Features           | N/A                |