Add config property for http2 by default

samples/grpc-tomcat-secure/src/main/resources/application.properties

@@ -1,5 +1,4 @@
 spring.application.name=grpc-tomcat-secure
 server.port=9090
-server.http2.enabled=true
 spring.security.user.name=user
 spring.security.user.password=user

samples/grpc-tomcat/src/main/resources/application.properties

@@ -1,6 +1,5 @@
 spring.application.name=grpc-tomcat
 server.port=9090
-server.http2.enabled=true
 logging.pattern.level=%5p [${spring.application.name:},%X{traceId:-},%X{spanId:-}]
 logging.level.org.springframework.security=DEBUG
 management.endpoints.web.exposure.include=*