ci: enable fuzzing workflow

Fuzzing workflow has been disabled due to warnings (treated by errors)
on compilation with Clang 14 that is used as a default compiler in
OSS-Fuzz infrastructure and missed libunwind in a test env where fuzzers
run. Compilation warnings were fixed in a previous commit and problem
with missed libunwind library has been resolved by patch to OSS-Fuzz
[1].

Follows up #6681

1. https://github.com/google/oss-fuzz/pull/7110

.github/workflows/fuzzing.yml

@@ -13,11 +13,6 @@ on:
 
 jobs:
   fuzzing:
-    # This workflow is disabled.
-    # See #6681 for details. Also, this comment
-    # https://github.com/tarantool/tarantool/pull/6764#issuecomment-1004616730
-    if: false
-
     runs-on: ubuntu-18.04
 
     strategy: