game entry file names changed to canonical version

games/openrct2.md

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+# OpenRCT2
+
+_Re-implementation of RollerCoaster Tycoon 2 (RCT2), expanding the game with new features, fixing original bugs and raising game limits._
+
+- Home: https://openrct2.io/, https://openrct2.org/ 
+- Media: https://en.wikipedia.org/wiki/RollerCoaster_Tycoon_2#Development
+- State: mature
+- Download: https://openrct2.org/downloads
+- Platform: Windows, Linux, macOS
+- Keywords: simulation, remake, requires original content (from RCT2)
+- Code repository: https://github.com/OpenRCT2/OpenRCT2.git
+- Code language: C++
+- Code license: GPL-3.0
+
+## Building
+
+- Build system: CMake