Remove spring.provides files

[elefeint]

Spring Boot removed spring.provides files from their starters (spring-projects/spring-boot#12435), since these files are only ever used by Spring Tool suite.

There is also a similar, albeit less conclusive, discussion in spring-attic/spring-ide#251.

@artembilan @meltsufin Should we remove it?

[artembilan]

Since commit message says Remove, then we just need to proceed with the current recommendation.

So, I'm considering this as not a question, but as an improvement.
In the end our starters should become as simple as just one POM file 😄

[meltsufin]

+1