fix: Remove V8_DEPRECATION_WARNINGS define to fix build with GCC <= 12

[timfish]

Building this module against the Electron ≥ 43 headers fails on Linux with stock GCC on Ubuntu 22.04 / Debian 12 (see the failing E2E Tests (ubuntu-22.04, 43.2.0, *) jobs in getsentry/sentry-electron#1398):

/home/runner/.electron-gyp/43.2.0/include/node/v8config.h:854:20: error: expected identifier before '__attribute__'
  854 | # define V8_EXPORT __attribute__((visibility("default")))
/home/runner/.electron-gyp/43.2.0/include/node/v8-primitive.h:658:4: error: expected primary-expression before 'public'

Electron 43 ships V8 15.0, where v8::String::Value now carries a class-level deprecation (v8-primitive.h:655):

class V8_DEPRECATED(
    "Prefer using String::ValueView if you can, or string->Write to a "
    "buffer if you cannot.") V8_EXPORT Value {

node-gyp's addon.gypi compiles all addons with -DV8_DEPRECATION_WARNINGS=1, so this expands to class [[deprecated("…")]] __attribute__((visibility("default"))) Value — a C++11 attribute mixed with a GNU attribute in a class head, which GCC ≤ 12 cannot parse (in either attribute order). GCC 13+ and clang parse it fine. The same declaration is still on V8 main, so this will also hit Node.js once it ships V8 15.

This PR strips the V8_DEPRECATION_WARNINGS=1 define via a defines! exclusion so the V8_DEPRECATED macros expand to nothing, restoring builds on GCC ≤ 12. The trade-off is that builds of this module no longer emit V8 API deprecation warnings.

Verified in Docker (node:20-bookworm, GCC 12.2) with node-gyp rebuild --target=43.2.0 --dist-url=https://electronjs.org/headers: reproduces the exact error before this change, builds cleanly after.