revert: docs(README.md): remove obsolete links to portable builds for windows

Revert commit 477ac5b5db.

Apparently those links aren't obsolete.

README.md

@@ -19,6 +19,8 @@ running on all major platforms.**
 * **Windows**:
   - [**64 bit installer**](https://build.tox.chat/view/qtox/job/qTox_pkg_windows_x86-64_stable_release/lastSuccessfulBuild/artifact/setup-qtox.exe)
   - [**32 bit installer**](https://build.tox.chat/view/qtox/job/qTox_pkg_windows_x86_stable_release/lastSuccessfulBuild/artifact/setup-qtox.exe)
+  - [**64 bit portable**](https://build.tox.chat/job/qTox_build_windows_x86-64_release/lastSuccessfulBuild/artifact/qTox_build_windows_x86-64_release.zip)
+  - [**32 bit portable**](https://build.tox.chat/job/qTox_build_windows_x86_release/lastSuccessfulBuild/artifact/qTox_build_windows_x86_release.zip)
 * **Linux**:
   - [**64 bit download**](https://build.tox.chat/view/Clients/job/qTox_build_linux_x86-64_release/lastSuccessfulBuild/artifact/qTox_build_linux_x86-64_release.tar.xz)
   - [**32 bit download**](https://build.tox.chat/view/Clients/job/qTox_build_linux_x86_release/lastSuccessfulBuild/artifact/qTox_build_linux_x86_release.tar.xz)