Delete start_impl.{cpp,h}

These files were unused.

Author: Databean

base/cvd/cuttlefish/host/commands/cvd/cli/commands/BUILD.bazel

@@ -482,14 +482,12 @@ clang_tidy_test(
 cc_library(
  name = "leaf_commands",
  srcs = [
- "start_impl.cpp",
  "status.cpp",
  "stop.cpp",
  "try_acloud.cpp",
  "version.cpp",
  ],
  hdrs = [
- "start_impl.h",
  "status.h",
  "stop.h",
  "try_acloud.h",