[FIX] type error when exporting to tarfiles

When exporting to a tarfile, we first export each module's translations
to a file on the FS, then create a tarball from all of them.

With the P3 bytes/string split, translation export was defined to export
to a bytes IO object in order to work correctly with CSV (which work on
bytes IO for better cross-version compatibility). However the tgz file
export was left opening module's files in `w` mode, which in P3 means
text, which blows up as POFile expects to ultimately write to a bytes IO
object: it uses text, and a StreamReaderWriter is used to translate that
into an underlying bytes IO.

Fix by explicitly opening the files in binary mode.

Fixes #22700

odoo/tools/translate.py

@@ -696,7 +696,7 @@ def trans_export(lang, modules, buffer, format, cr):
                 tmpmoddir = join(tmpdir, mod, 'i18n')
                 os.makedirs(tmpmoddir)
                 pofilename = (lang if lang else mod) + ".po" + ('t' if not lang else '')
-                buf = open(join(tmpmoddir, pofilename), 'w')
+                buf = open(join(tmpmoddir, pofilename), 'wb')
                 _process('po', [mod], modrows, buf, lang)
                 buf.close()