Ignore deleted files in python format checks (#14210)

Add `--diff-filter=d` in `git diff` to ignore deleted files when
checking formats; otherwise `black` will fail to find the deleted files.

`d` means deleted and lowercase means to exclude.

skip-ci: Not run in CI workflow

.github/workflows/lint.yml

diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index e1b3835..4afd829 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -64,7 +64,9 @@
           python3 -m pip install black==23.3
       - name: Check if modified files are formatted
         run: |
-          git diff "${GITHUB_BASE_REF?}" --name-only -- '*.py' ':!third_party' \
+          # The filter lowercase `d` means to exclude deleted files.
+          git diff "${GITHUB_BASE_REF?}" --name-only --diff-filter=d \
+            -- '*.py' ':!third_party' \
             | xargs --no-run-if-empty black --check --diff --verbose
       - name: Instructions for fixing the above linting errors
         if: failure()

build_tools/scripts/lint.sh

diff --git a/build_tools/scripts/lint.sh b/build_tools/scripts/lint.sh
index f7f3ca2..68cd2a6 100755
--- a/build_tools/scripts/lint.sh
+++ b/build_tools/scripts/lint.sh
@@ -55,7 +55,9 @@
 git diff --exit-code
 
 echo "***** black *****"
-git diff main --name-only -- '*.py' ':!third_party' | xargs -r black
+# The filter lowercase `d` means to exclude deleted files.
+git diff main --name-only --diff-filter=d -- '*.py' ':!third_party' \
+  | xargs -r black
 
 echo "***** pytype *****"
 ./build_tools/pytype/check_diff.sh