build: avoid redefined macro

It's already defined in `common.gypi`.

PR-URL: #45544
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Daeyeon Jeong <daeyeon.dev@gmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

tools/icu/icu-generic.gyp

@@ -93,7 +93,6 @@
         },
         'defines': [
           'U_ATTRIBUTE_DEPRECATED=',
-          '_CRT_SECURE_NO_DEPRECATE=',
           'U_STATIC_IMPLEMENTATION=1',
         ],
       },