v2.4.x: Update Alire version and use ubuntu-18.04 for building

.github/workflows/ada.yml

@@ -9,7 +9,7 @@ on:
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
 
     steps:
     - name: Checkout

alire.toml

@@ -1,6 +1,6 @@
 name = "asfml"
 description = "ASFML is an Ada binding to SFML, the Simple and Fast Multimedia Library"
-version = "2.5.3"
+version = "2.4.1"
 
 authors = ["Manuel Gomez", "Dan Lee Vazquez Garcia"]
 maintainers = ["Manuel Gomez <[email protected]>"]
@@ -11,4 +11,4 @@ website = "https://mgrojo.github.io/ASFML/"
 tags = ["audio", "games", "opengl", "cross-platform", "multimedia", "binding", "graphics", "sfml"]
 
 [[depends-on]]
-libcsfml = "^2.5"
+libcsfml = "^2.4"