spring starter's LogbackAppenderInstaller still needs to be updated to use declarative config somehow

[zeitlinger]

from #15599

• spring starter's LogbackAppenderInstaller still needs to be updated to use declarative config somehow
  • it's supported already using

    opentelemetry-java-instrumentation/instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/internal/instrumentation/logging/LogbackAppenderInstaller.java

    Line 244 in 76e8527

    EarlyConfig.translatePropertyName(environment, property), Boolean.class);

• also delete DeprecatedConfigProperties and only accept the new value
  • it's experimental, so we don't need to wait for 3.0