Switch to Yahoo for OIDC as Google's cert is not yet trusted by Java 11

Until the fix for JDK-8209506 [1] is available in Java 11 builds,
SSL connections to services using Google's SSL certificate do not work
due to a lack of trust. This affects both our OAuth2 client samples
which were using https://accounts.google.com as an OpenID Connect
provider.

This commit switches the two samples to use Yahoo in place of Google.

See gh-14028

[1] https://bugs.openjdk.java.net/browse/JDK-8209506

spring-boot-samples/spring-boot-sample-oauth2-client/src/main/resources/application.yml

@@ -17,9 +17,9 @@ spring:
             provider: github
             scope: user:email
             redirect-uri-template: http://localhost:8080/login/oauth2/code/github
-          google-oidc:
-            client-id: ${GOOGLE-CLIENT-ID}
-            client-secret: ${GOOGLE-CLIENT-SECRET}
+          yahoo-oidc:
+            client-id: ${YAHOO-CLIENT-ID}
+            client-secret: ${YAHOO-CLIENT-SECRET}
         provider:
-          google-oidc:
-            issuer-uri: https://accounts.google.com
+          yahoo-oidc:
+            issuer-uri: https://api.login.yahoo.com/