ARROW-6725: [CI] Disable 3rdparty fuzzit nightly builds

@yevgenypats I've created a follow-up issue where we can discuss how should we reliably execute the fuzzit job https://issues.apache.org/jira/browse/ARROW-6726

Closes #5528 from kszucs/disable-fuzzit-nightly and squashes the following commits:

440a300 <Krisztián Szűcs> disable fuzzit nightly builds

Authored-by: Krisztián Szűcs <szucs.krisztian@gmail.com>
Signed-off-by: Wes McKinney <wesm+git@apache.org>

dev/tasks/tasks.yml

@@ -80,7 +80,6 @@ groups:
     - docker-cpp-alpine
     - docker-cpp-cmake32
     - docker-cpp-release
-    - docker-cpp-fuzzit
     - docker-cpp-static-only
     - docker-c_glib
     - docker-go
@@ -174,7 +173,6 @@ groups:
     - docker-cpp
     - docker-cpp-cmake32
     - docker-cpp-release
-    - docker-cpp-fuzzit
     - docker-cpp-static-only
     - docker-c_glib
     - docker-go