OZG-6810 remove unused methods

vorgang-manager-server/pom.xml

...e/ozgcloud/vorgang/VorgangManagerServerConfiguration.java

...ang/command/PersistPostfachNachrichtByCommandService.java

.../src/main/java/de/ozgcloud/vorgang/files/FileService.java

...java/de/ozgcloud/vorgang/files/GrpcBinaryFileService.java

.../de/ozgcloud/nachrichten/postfach/PostfachMailITCase.java

.../src/test/java/de/ozgcloud/processor/ProcessorITCase.java

...e/ozgcloud/vorgang/command/AttachmentFileTestFactory.java

...command/PersistPostfachNachrichtByCommandServiceTest.java

.../test/java/de/ozgcloud/vorgang/files/FileServiceTest.java

.../de/ozgcloud/vorgang/files/GrpcBinaryFileServiceTest.java