Add FIELD annotation target to @ActivityContext qualifier.

If the qualifiers does not have the target field then it can't
be used with in members that are injected either by entry points
or @androidentrypoint.

This change also removes the @target(TYPE) the annotation contained,
this was a mistake and there is no reason for this qualifier to be
added to a class definition.

Fixes #1980

RELNOTES=Added missing FIELD target to @ActivityContext qualifier.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=320698031

java/dagger/hilt/android/qualifiers/ActivityContext.java

@@ -22,10 +22,8 @@
 import java.lang.annotation.Target;
 import javax.inject.Qualifier;
 
-/**
- * Annotation for a {@code Context} that corresponds to the activity.
- */
+/** Annotation for a {@code Context} that corresponds to the activity. */
 @Qualifier
 @Retention(RetentionPolicy.CLASS)
-@Target({ElementType.TYPE, ElementType.METHOD, ElementType.PARAMETER})
+@Target({ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD})
 public @interface ActivityContext {}