message: refactor(animations): remove the unused enter and leave selectors
  remove the no longer used ENTER_SELECTOR and LEAVE_SELECTOR constants
  note: their uses have been removed in PR
  PR Close
diff: @@ -9,7 +9,7 @@ import {AnimateTimings, AnimationAnimateChildMetadata, AnimationAnimateMetadata,
  import {AnimationDriver} from '../render/animation_driver';
  import {getOrSetAsInMap} from '../render/shared';
  -import {copyObj, ENTER_SELECTOR, extractStyleParams, iteratorToArray, LEAVE_SELECTOR, NG_ANIMATING_SELECTOR, NG_TRIGGER_SELECTOR, normalizeAnimationEntry, resolveTiming, SUBSTITUTION_EXPR_START, validateStyleParams, visitDslNode} from '../util';
  +import {copyObj, extractStyleParams, iteratorToArray, NG_ANIMATING_SELECTOR, NG_TRIGGER_SELECTOR, normalizeAnimationEntry, resolveTiming, SUBSTITUTION_EXPR_START, validateStyleParams, visitDslNode} from '../util';
  import {AnimateAst, AnimateChildAst, AnimateRefAst, Ast, DynamicTimingAst, GroupAst, KeyframesAst, QueryAst, ReferenceAst, SequenceAst, StaggerAst, StateAst, StyleAst, TimingAst, TransitionAst, TriggerAst} from './animation_ast';
  import {AnimationDslVisitor} from './animation_dsl_visitor';
  