chore: update spring-boot to 2.6.2

[Artur-]

No description provided.

[Artur-]

Fails in test-ts-services with

[14:54:37] :	 [Step 3/7] 2021-11-29 12:54:37.103  WARN 5606 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'requestMappingHandlerMapping' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Invocation of init method failed; nested exception is java.lang.NullPointerException

[platosha]

Fails in test-ts-services with

[14:54:37] :	 [Step 3/7] 2021-11-29 12:54:37.103  WARN 5606 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'requestMappingHandlerMapping' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Invocation of init method failed; nested exception is java.lang.NullPointerException

Seems that we need to support the PathPattern based mapping to fix this, here is the PR vaadin/flow#12474

[Artur-]

The next problem seems to be

java.lang.AbstractMethodError: Receiver class org.springframework.boot.web.servlet.filter.ErrorPageSecurityFilter does not define or inherit an implementation of the resolved method 'abstract void init(javax.servlet.FilterConfig)' of interface javax.servlet.Filter.

when running the app as a war using jetty:run

[Artur-]

spring-projects/spring-boot#28854