sdl2: Update submodule to 845c7e2

Ryzee119 · Ryzee119 · commit 631015c1b2e4 · 2021-05-04T16:42:07.000+09:30
diff --git a/lib/sdl/SDL2 b/lib/sdl/SDL2
@@ -1 +1 @@
-Subproject commit a2a2d9ca1a5a7082c830490a0b110829939de3a7
+Subproject commit 845c7e2f4631db2cb5d7bab1aaf5ba56c8fe86cf
