Pin API Fuzzing version to 1.6

ee/changelogs/unreleased/327510-pin-apifuzzing-version.yml

+---
+title: Set API Fuzzing version to 1.6 in CI template
+merge_request: 59181
+author:
+type: changed

lib/gitlab/ci/templates/Security/API-Fuzzing.gitlab-ci.yml

@@ -12,7 +12,7 @@ stages:
 
 variables:
     FUZZAPI_PROFILE: Quick
-    FUZZAPI_VERSION: latest
+    FUZZAPI_VERSION: "1.6"
     FUZZAPI_CONFIG: .gitlab-api-fuzzing.yml
     FUZZAPI_TIMEOUT: 30
     FUZZAPI_REPORT: gl-api-fuzzing-report.json