Fix stale doc regarding `null`-ness

(Both the getter and the constructor parameters annotated `@NonNull`,
but doc says `null`)

Bug: n/a
Test: existing
Change-Id: I091b47e6d789ad5d767de12e9aff34c85791dbd4
diff --git a/lint/libs/lint-api/src/main/java/com/android/tools/lint/detector/api/Implementation.java b/lint/libs/lint-api/src/main/java/com/android/tools/lint/detector/api/Implementation.java
index edf967a..e1054b1 100644
--- a/lint/libs/lint-api/src/main/java/com/android/tools/lint/detector/api/Implementation.java
+++ b/lint/libs/lint-api/src/main/java/com/android/tools/lint/detector/api/Implementation.java
@@ -117,7 +117,7 @@
      * <p>NOTE: You would normally call {@link #isAdequate(EnumSet)} rather than calling this method
      * directly.
      *
-     * @return a list of required scopes, or null.
+     * @return a list of required scopes.
      */
     @NonNull
     public EnumSet<Scope>[] getAnalysisScopes() {