[libFuzzer] Remove extra semicolons

Summary:
Remove extra semicolons so that libFuzzer can compile with
-Werror -Wextra-semi

Reviewers: Dor1s, morehouse, thakis

Reviewed By: Dor1s, morehouse

Subscribers: jdoerfert, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D58674

llvm-svn: 354902