kraft.yaml: Update dependencies versions

Change all the versions to "stable" for better compatibility.

Signed-off-by: Darius-Andrei Jipa <jipad16@yahoo.com>
Reviewed-by: Eduard Vintilă <eduard.vintila47@gmail.com>
Reviewed-by: Stefan Jumarea <stefanjumarea02@gmail.com>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #9

kraft.yaml

@@ -5,14 +5,14 @@ targets:
   - architecture: x86_64
     platform: linuxu
   - architecture: x86_64
-    platform: kvm
+    platform: qemu
   - architecture: x86_64
     platform: xen
 libraries:
   musl:
-    version: stable
+    version: 'stable'
   lua:
-    version: '0.13.1'
+    version: 'stable'
     kconfig:
       - CONFIG_LIBLUA=y
       - CONFIG_LIBLUA_MAIN_FUNCTION=y