tunnel: also bump the minsdk of this module

Fixes: 3b6ab66 ("ui: raise min SDK to 24")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Author: zx2c4

tunnel/build.gradle.kts

@@ -19,7 +19,7 @@ android {
     }
     namespace = "${pkg}.tunnel"
     defaultConfig {
-        minSdk = 21
+        minSdk = 24
     }
     externalNativeBuild {
         cmake {