migrate to clap 3.x

Bug: 229854484
Test: atest
Change-Id: Iae1ad1b5f7c2832c11bf2db09e7985ddaaf927d4
diff --git a/zipfuse/src/main.rs b/zipfuse/src/main.rs
index 874056a..8400a72 100644
--- a/zipfuse/src/main.rs
+++ b/zipfuse/src/main.rs
@@ -41,7 +41,7 @@
     let matches = App::new("zipfuse")
         .arg(
             Arg::with_name("options")
-                .short("o")
+                .short('o')
                 .takes_value(true)
                 .required(false)
                 .help("Comma separated list of mount options"),