CI: Un-integrate CIFuzz

Referring to the conversation in
https://github.com/google/oss-fuzz/issues/7479 and #559, there was a
misunderstanding regarding how CIFuzz works.  It cannot be used to fuzz
arbitrary PRs or code branches, and it has a 90-day delay in downloading
corpora from OSS-Fuzz.  That makes it unsuitable for libjpeg-turbo.

.github/workflows/cifuzz.yml

@@ -1,35 +0,0 @@
-name: CIFuzz
-
-on:
-  push:
-    branches:
-      - '**'
-    tags-ignore:
-      - '**'
-  pull_request:
-  workflow_dispatch:
-
-jobs:
-  Fuzzing:
-    runs-on: ubuntu-latest
-    steps:
-    - name: Build Fuzzers
-      id: build
-      uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
-      with:
-        oss-fuzz-project-name: 'libjpeg-turbo'
-        dry-run: false
-        language: c
-    - name: Run Fuzzers
-      uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
-      with:
-        oss-fuzz-project-name: 'libjpeg-turbo'
-        fuzz-seconds: 600
-        language: c
-        dry-run: false
-    - name: Upload Crash
-      uses: actions/upload-artifact@v1
-      if: failure() && steps.build.outcome == 'success'
-      with:
-        name: artifacts
-        path: ./out/artifacts