cmake: bump luzer version

The patch bumps a luzer's version, full list of commits is in [1].
Notable changes are:

- Added support LuaCov.
- Added support Address and UndefinedBehaviour sanitizers.
- Method `oneof()` in FuzzedDataProvider returns an item's index
  as a second value.
- Fixed a memory leak in a Lua-based implementation of `TestOneInput()`.
- An initial buffer size in FuzzedDataProvider.

1. ligurio/luzer@82d41c5...3f4eb03

Needed for #135

Author: ligurio

cmake/BuildLuzer.cmake

@@ -26,7 +26,7 @@ endif()
 
 ExternalProject_Add(bundled-luzer
     GIT_REPOSITORY https://github.com/ligurio/luzer
-    GIT_TAG 82d41c5f350296ca351e785a24c914165a0e8033
+    GIT_TAG 3f4eb03b4ff7596855a0aaf45aa557f61b25ddb2
     GIT_PROGRESS TRUE
     GIT_SHALLOW FALSE
     SOURCE_DIR ${LUZER_DIR}/source