ci: remove spell_check

We often get wrong report when documentation related are
changed, such as:

```
Getting action download info
Error: This request has been automatically failed because
it uses a deprecated version of `actions/download-artifact: v3`.
Learn more: https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/.
This request has been automatically failed because it uses
a deprecated version of `actions/upload-artifact: v3`.
Learn more: https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/
```

Just remove this action till now.

Signed-off-by: Chen Wang <unicorn_wang@outlook.com>

.github/workflows/spell_check.yml

@@ -1,34 +0,0 @@
-name: Check Spelling
-
-on:
-  pull_request:
-    branches:
-      - master
-    paths:
-      - 'documentation/**'
-jobs:
-  spelling:
-    name: Check Spelling
-    runs-on: ubuntu-22.04
-    if: github.repository_owner == 'RT-Thread'
-    steps:
-    - name: output ignore words info
-      run: |
-        echo "> If any words shown as incorrect are spelled correctly, please add them to .github/actions/spelling/allow.txt." >> $GITHUB_STEP_SUMMARY
-    - name: check spelling
-      id: spelling
-      uses: check-spelling/check-spelling@v0.0.20
-      with:
-        checkout: true
-        check_file_names: 0
-        only_check_changed_files: 1
-        post_comment: 0
-        extra_dictionaries:
-          cspell:en_US/src/en_US.txt
-          cspell:software-terms/softwareTerms.txt
-          cspell:python/python.txt
-          cspell:cpp/cpp.txt
-        check_extra_dictionaries: ''
-    - name: output Success info
-      run: |
-        echo "✅ Check spelling success." >> $GITHUB_STEP_SUMMARY