www/qt6-webengine: Switch to bundled re2

• Prepare the port for newer versions of devel/re2, which also require devel/abseil. This combination however causes build errors [1] due to missing symbols:

[...]
In file included from gen/extensions/browser/browser_sources_jumbo_8.cc:6:
./../../../../../qtwebengine-everywhere-src-6.5.2/src/3rdparty/chromium/extensions/browser/api/web_request/form_data_parser.cc:429:11: error: no member named 'set' in 'absl::string_view'

source_.set(source.data(), source.size());
~~~~~~~ ^

./../../../../../qtwebengine-everywhere-src-6.5.2/src/3rdparty/chromium/extensions/browser/api/web_request/form_data_parser.cc:573:11: error: no member named 'set' in 'absl::string_view'

source_.set(source.data(), source.size());
~~~~~~~ ^

[...]

Unbundling abseil and its-subcomponents via "replace_gn_files.py" didn't
help hence switch to the bundled re2 for now to have a consistent
combination of re2 and abseil.

• Bump PORTREVISION due dependency change.

PR: 260402 [1]
Reported by: diizzy [1]
Reviewed by: diizzy, tcberner
Differential Revision: https://reviews.freebsd.org/D41571