builtin/repack.c: clean up unused `#include`s

Over the past several dozen commits, we have moved a large amount of
functionality out of the repack builtin and into other files like
repack.c, repack-cruft.c, repack-filtered.c, repack-midx.c, and
repack-promisor.c.

These files specify the minimal set of `#include`s that they need to
compile successfully, but we did not change the set of `#include`s in
the repack builtin itself.

Now that the code movement is complete, let's clean up that set of
`#include`s and trim down the builtin to include the minimal amount of
external headers necessary to compile.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/repack.c

@@ -4,26 +4,17 @@
 #include "builtin.h"
 #include "config.h"
 #include "environment.h"
-#include "gettext.h"
-#include "hex.h"
 #include "parse-options.h"
 #include "path.h"
 #include "run-command.h"
 #include "server-info.h"
-#include "strbuf.h"
 #include "string-list.h"
-#include "strvec.h"
 #include "midx.h"
 #include "packfile.h"
 #include "prune-packed.h"
-#include "odb.h"
 #include "promisor-remote.h"
 #include "repack.h"
 #include "shallow.h"
-#include "pack.h"
-#include "pack-bitmap.h"
-#include "refs.h"
-#include "list-objects-filter-options.h"
 
 #define ALL_INTO_ONE 1
 #define LOOSEN_UNREACHABLE 2