fix(reader_xlsx): add missing import subprocess

`_x_recalc_copy` calls `subprocess.run` twice but the module never imports
`subprocess`. Because the whole body is wrapped in `except Exception: return
None`, the resulting `NameError` is swallowed silently: whenever LibreOffice
(`soffice`) is actually installed, the recalc path raises, returns None, and the
workbook is marked "soffice unavailable" — so the formula-recalc feature never
works even when it could.

Author: Anai-Guo

plugins/tools/_reader_xlsx.py

@@ -15,6 +15,7 @@
 import os
 import re
 import shutil
+import subprocess
 import tempfile
 import xml.etree.ElementTree as _ET
 import zipfile