Fix if-let

It should be `=` and not `=>`, at least as of current stable Rust.

Author: snyball

rust-mode/if-let

@@ -3,6 +3,6 @@
 # key: ifl
 # uuid: ifl
 # --
-if let ${1:Some(${2:x})} => ${3:var} {
+if let ${1:Some(${2:x})} = ${3:var} {
    `%`$0
-}
+}