Remove outdated windows CI information

The CONTRIBUTING.md file states that our CI does not run regression
checks on Windows, which is outdated information. In fact, we do execute
regression checks on Windows in our current CI. This pull request
removes the outdated section.

Author: jnidzwetzki

CONTRIBUTING.md

@@ -124,26 +124,3 @@ All submitted pull requests are also automatically
 run against our test suite via [Github Actions](https://github.com/timescale/timescaledb/actions)
 (that link shows the latest build status of the repository).
 
-## Advanced Topics
-
-### Testing on Windows
-
-Currently our CI infrastructure only ensures that TimescaleDB builds on
-Windows, but does not run regression tests due to differences between
-Unix-based systems and Windows. We do run these tests before releases
-manually, and it would be a bonus if you could test at least non-trivial
-contributions for Windows. This involves setting up a remote Windows machine
-with TimescaleDB and a Unix-based (e.g., macOS or Linux) machine
-to serve as the client. To set up the Windows machine, build from source:
-```bash
-./bootstrap -DCMAKE_BUILD_TYPE=Debug
-cmake --build ./build --config Debug
-cmake --build ./build --config Debug --target install
-```
-
-Then on the client machine:
-```bash
-./bootstrap -DCMAKE_BUILD_TYPE=Debug -DTEST_PGHOST=ip_addr_of_Win_machine
-cd build && make
-make installchecklocal
-```