Doc: Supported Platforms: Update Windows reference platforms

Continuous integration tests are run on MSVC 2017 (both 32 and 64-bit)
platforms. Windows 8.1/MSVC 2013 (32-bit) is not CI-tested.

Change-Id: Id66659fd06693eeb95e9375753c092dccb44a15a
Reviewed-by: Heikki Halmet <heikki.halmet@qt.io>

doc/src/platforms/supported-platforms.qdocinc

@@ -48,16 +48,16 @@ Mobile Platforms: \l {Qt for Android}{Android},
     \header \li Platform \li Compiler \li Notes
     \header \li {3,1} \l {Qt for Windows}{Windows}
     \row \li Windows 10 (64-bit)
-         \li MSVC 2017, \b {MSVC 2015}, MSVC 2013, MinGW 5.3
+         \li \b {MSVC 2017}, \b {MSVC 2015}, MSVC 2013, MinGW 5.3
          \li
     \row \li Windows 10 (32-bit)
-         \li MSVC 2017, \b {MSVC 2015}, MSVC 2013, MinGW 5.3
+         \li \b {MSVC 2017}, \b {MSVC 2015}, MSVC 2013, MinGW 5.3
          \li
     \row \li Windows 8.1 (64-bit)
          \li MSVC 2017, MSVC 2015, \b {MSVC 2013}, MinGW 5.3
          \li
     \row \li Windows 8.1 (32-bit)
-         \li MSVC 2017, MSVC 2015, \b {MSVC 2013}, MinGW 5.3
+         \li MSVC 2017, MSVC 2015, MSVC 2013, MinGW 5.3
          \li
     \row \li Windows 7 (64-bit)
          \li MSVC 2017, MSVC 2015, MSVC 2013, \b {MinGW 5.3}