Update system requirements for ruby

docs/codeql/codeql-overview/system-requirements.rst

@@ -35,3 +35,7 @@ For Python extraction:
 - On Linux and macOS, Python 3 must be installed and available on the ``PATH`` as ``python3`` or ``python``.
 - For Python 2 extraction on Linux and macOS, we also recommend having Python 2 installed and available on the ``PATH`` as ``python2``.
 - On Windows, the Python launcher must be installed and available on the ``PATH`` as ``py.exe``.
+
+For Ruby extraction:
+
+- On Windows, the ``msvcp140.dll`` must be installed and available in the system. This can be installed by downloading the appropriate Microsoft Visual C++ Redistributable for Visual Studio.