ci(windows): run the docs step under bash

The Windows job's default shell is pwsh, where a trailing backslash is
not a line continuation. It parsed --exclude as a unary operator and the
step failed before cargo ran, which is how the job this PR adds the step
to went red.

bash rather than folding the command onto one line, so it stays
byte-identical to the Linux rustdoc job it exists to mirror.

Author: yuzi-co

.github/workflows/ci.yml

@@ -313,6 +313,10 @@ jobs:
       - name: cargo doc
         env:
           RUSTDOCFLAGS: "-D warnings"
+        # This job's default shell is pwsh, where a trailing backslash is not a
+        # line continuation and `--exclude` parses as a unary operator. bash keeps
+        # this command byte-identical to the Linux rustdoc job it mirrors.
+        shell: bash
         run: |
           cargo doc --workspace --no-deps --document-private-items \
             --exclude openlogi-ui \