test(spec): drop policies↔policy mapping assertions after PolicySchema removal

metadata-collection.test.ts asserted the now-removed `policies`/`policy`
collection alias (PLURAL_TO_SINGULAR / pluralToSingular / singularToPlural).
Full spec suite (6595) now green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: os-zhuang

packages/spec/src/shared/metadata-collection.test.ts

@@ -288,7 +288,6 @@ describe('PLURAL_TO_SINGULAR / SINGULAR_TO_PLURAL', () => {
   });
 
   it('should map irregular plural forms correctly', () => {
-    expect(PLURAL_TO_SINGULAR['policies']).toBe('policy');
     expect(PLURAL_TO_SINGULAR['sharingRules']).toBe('sharing_rule');
     expect(PLURAL_TO_SINGULAR['analyticsCubes']).toBe('analytics_cube');
     expect(PLURAL_TO_SINGULAR['ragPipelines']).toBe('rag_pipeline');
@@ -304,7 +303,6 @@ describe('PLURAL_TO_SINGULAR / SINGULAR_TO_PLURAL', () => {
 describe('pluralToSingular', () => {
   it('should convert known plural to singular', () => {
     expect(pluralToSingular('apps')).toBe('app');
-    expect(pluralToSingular('policies')).toBe('policy');
     expect(pluralToSingular('sharingRules')).toBe('sharing_rule');
   });
 
@@ -317,7 +315,6 @@ describe('pluralToSingular', () => {
 describe('singularToPlural', () => {
   it('should convert known singular to plural', () => {
     expect(singularToPlural('app')).toBe('apps');
-    expect(singularToPlural('policy')).toBe('policies');
     expect(singularToPlural('sharing_rule')).toBe('sharingRules');
   });