Fix 1 occurrence of if-begin-to-cond

Using `cond` instead of `if` here makes `begin` unnecessary

Author: resyntax-ci[bot]

typed-racket-test/optimizer/transform.rkt

@@ -33,13 +33,12 @@
       (for ((entry new-tr-log))
         (write-stringln entry))
       (write-stringln "END")
-      (if (regexp-match "\n" new-output)
-          (begin
-            (write-stringln "#<<END")
-            (write-stringln new-output)
-            (write-stringln "END"))
-          (begin
-            (write new-output)))
+      (cond
+        [(regexp-match "\n" new-output)
+         (write-stringln "#<<END")
+         (write-stringln new-output)
+         (write-stringln "END")]
+        [else (write new-output)])
           (write-string source-code))))
 
 ;; proc returns the list of tests to be run on each file