upgrade to 1.3

Flatpak specific
 drop configure changes as they are no longer needed?
 bump to freedesktop 21.08
 removed OpenGL_GL_PREFERENCE unused variable
 fix my mistake with adding rc1 upstream :(
   (hughsie/appstream-glib#417)

disable-largest-icon.patch

@@ -8,6 +8,5 @@ index 99b285dd6..c06c5c7b9 100644
  install(FILES data/supertuxkart_512.png DESTINATION share/icons/hicolor/512x512/apps RENAME supertuxkart.png)
 -install(FILES data/supertuxkart_1024.png DESTINATION share/icons/hicolor/1024x1024/apps RENAME supertuxkart.png)
 +#install(FILES data/supertuxkart_1024.png DESTINATION share/icons/hicolor/1024x1024/apps RENAME supertuxkart.png)
- install(FILES data/supertuxkart_512.png DESTINATION share/pixmaps RENAME supertuxkart.png)
  install(FILES data/supertuxkart.appdata.xml DESTINATION share/metainfo)
 

fix-app-data-versioning.patch

@@ -0,0 +1,14 @@
+diff --git a/data/supertuxkart.appdata.xml b/data/supertuxkart.appdata.xml
+index fc8d764..f53eec5 100644
+--- a/data/supertuxkart.appdata.xml
++++ b/data/supertuxkart.appdata.xml
+@@ -345,9 +345,6 @@
+     <release version="1.3" date="2021-09-28">
+       <url>https://blog.supertuxkart.net/2021/09/supertuxkart-13-release.html</url>
+     </release>
+-    <release version="1.3-rc1" date="2021-08-31">
+-      <url>https://blog.supertuxkart.net/2021/08/supertuxkart-13-release-candiate.html</url>
+-    </release>
+     <release version="1.2" date="2020-08-27"/>
+     <release version="1.1" date="2020-01-05"/>
+     <release version="1.0" date="2019-04-21"/>

net.supertuxkart.SuperTuxKart.json

@@ -2,7 +2,7 @@
     "app-id": "net.supertuxkart.SuperTuxKart",
     "default-branch": "stable",
     "runtime": "org.freedesktop.Platform",
-    "runtime-version": "20.08",
+    "runtime-version": "21.08",
     "sdk": "org.freedesktop.Sdk",
     "rename-desktop-file": "supertuxkart.desktop",
     "rename-appdata-file": "supertuxkart.appdata.xml",
@@ -42,16 +42,16 @@
         {
             "name": "supertuxkart",
             "buildsystem": "cmake-ninja",
-            "config-opts": ["-DUSE_WIIUSE=0", "-DOpenGL_GL_PREFERENCE=LEGACY" ],
+            "config-opts": ["-DUSE_WIIUSE=0" ],
             "sources": [
                 {
                     "type": "archive",
-                    "url": "https://downloads.sourceforge.net/project/supertuxkart/SuperTuxKart/1.2/SuperTuxKart-1.2-src.tar.xz",
-                    "sha256": "052edf0afdbeb99583fe8676fb0ab80ecb6103fb88b7540f858d1b5fa1297d37"
+                    "url": "https://github.com/supertuxkart/stk-code/releases/download/1.3/SuperTuxKart-1.3-src.tar.xz",
+                    "sha256": "eeabeb0d9801688a218f6f0a76ea3546a46a322ccaca9a258148ecacfe083ffd"
                 },
                 {
                     "type": "patch",
-                    "path": "fix-AppData-file.patch"
+                    "path": "fix-app-data-versioning.patch"
                 },
                 {
                     "type": "patch",