docs(appsync): fix "an unique" to "a unique" in JSDoc comments

"unique" starts with a consonant sound /juː/, so the correct
indefinite article is "a" (not "an").

Author: syukawa-dev

packages/aws-cdk-lib/aws-appsync/lib/eventapi.ts

@@ -513,7 +513,7 @@ export interface EventApiAttributes {
   readonly apiName?: string;
 
   /**
-   * an unique AWS AppSync Event API identifier
+   * a unique AWS AppSync Event API identifier
    * i.e. 'lxz775lwdrgcndgz3nurvac7oa'
    */
   readonly apiId: string;
@@ -579,7 +579,7 @@ export class EventApi extends EventApiBase {
   }
 
   /**
-   * an unique AWS AppSync Event API identifier
+   * a unique AWS AppSync Event API identifier
    * i.e. 'lxz775lwdrgcndgz3nurvac7oa'
    */
   public readonly apiId: string;

packages/aws-cdk-lib/aws-appsync/lib/graphqlapi-base.ts

@@ -171,7 +171,7 @@ export enum AuthorizationType {
 export interface IGraphqlApi extends IResource, IGraphQLApiRef {
 
   /**
-   * an unique AWS AppSync GraphQL API identifier
+   * a unique AWS AppSync GraphQL API identifier
    * i.e. 'lxz775lwdrgcndgz3nurvac7oa'
    *
    * @attribute
@@ -352,7 +352,7 @@ export interface IGraphqlApi extends IResource, IGraphQLApiRef {
  */
 export abstract class GraphqlApiBase extends Resource implements IGraphqlApi {
   /**
-   * an unique AWS AppSync GraphQL API identifier
+   * a unique AWS AppSync GraphQL API identifier
    * i.e. 'lxz775lwdrgcndgz3nurvac7oa'
    */
   public abstract readonly apiId: string;

packages/aws-cdk-lib/aws-appsync/lib/graphqlapi.ts

@@ -531,7 +531,7 @@ export interface GraphqlApiProps {
  */
 export interface GraphqlApiAttributes {
   /**
-   * an unique AWS AppSync GraphQL API identifier
+   * a unique AWS AppSync GraphQL API identifier
    * i.e. 'lxz775lwdrgcndgz3nurvac7oa'
    */
   readonly graphqlApiId: string;
@@ -621,7 +621,7 @@ export class GraphqlApi extends GraphqlApiBase {
   }
 
   /**
-   * an unique AWS AppSync GraphQL API identifier
+   * a unique AWS AppSync GraphQL API identifier
    * i.e. 'lxz775lwdrgcndgz3nurvac7oa'
    */
   public readonly apiId: string;