update-deps: skip bundled-gem object files in read_cc_deps

Mirrors the existing `.bundle/` filter in read_make_deps (line 330).
After ordering `ext/configure-ext.mk` after prepare-gems, bundled-gem
C extensions get compiled during the main build, so `Pathname.glob('**/*.o')`
picks up things like `.bundle/gems/bigdecimal-4.1.2/ext/bigdecimal/bigdecimal.o`.
Those targets then reach `in_makefile`, which has no case for `.bundle/`
paths and raises "unexpected target".

Bundled gems own their depend files, so they should be skipped here.

https://claude.ai/code/session_01YRoRyZPew2LtN6u6BX8bzx

Author: claude

tool/update-deps

@@ -401,6 +401,7 @@ end
 def read_cc_deps(cwd)
   deps = {}
   Pathname.glob('**/*.o').sort.each {|fn_o|
+    next if /\.bundle\// =~ fn_o.to_s # skip bundled gem extensions; they manage their own depend files
     fn_i = fn_o.sub_ext('.i')
     if !fn_i.exist?
       next if fn_o.sub_ext('.S').exist?