Fix md5sum for SDL3 recipe version 3.2.18 (kivy#3183)

* fix md5sum

* use lowercase

Author: DexerBR

pythonforandroid/recipes/sdl3/__init__.py

@@ -8,7 +8,7 @@
 class LibSDL3Recipe(BootstrapNDKRecipe):
     version = "3.2.18"
     url = "https://github.com/libsdl-org/SDL/releases/download/release-{version}/SDL3-{version}.tar.gz"
-    md5sum = "70cda886bcf5a4fdac550db796d2efa2"
+    md5sum = "c7808ef624b74e2ac69cf531e78e0c6e"
 
     conflicts = ["sdl2"]