build: remove nonexistent header from abseil.gyp

This header was removed in the V8 15.2 update, but its entry was left
behind in the gyp source list.

Signed-off-by: Jiawen Geng <technicalcute@gmail.com>
Assisted-by: claude:opus-5.5
PR-URL: #66583
Reviewed-By: Richard Lau <richard.lau@ibm.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

Author: gengjiawen

tools/v8_gypfiles/abseil.gyp

@@ -261,7 +261,6 @@
         '<(ABSEIL_ROOT)/absl/strings/internal/pow10_helper.h',
         '<(ABSEIL_ROOT)/absl/strings/internal/pow10_helper.cc',
         '<(ABSEIL_ROOT)/absl/strings/internal/resize_uninitialized.h',
-        '<(ABSEIL_ROOT)/absl/strings/internal/stl_type_traits.h',
         '<(ABSEIL_ROOT)/absl/strings/internal/str_format/arg.h',
         '<(ABSEIL_ROOT)/absl/strings/internal/str_format/arg.cc',
         '<(ABSEIL_ROOT)/absl/strings/internal/str_format/bind.h',