Upgrade xlrd to version 2

xlrd is a library for reading data and formatting information from
Excel files in the historical .xls format.

Version 2 of xlrd no longer supports anything other than .xls files.

We were using it to also support reading .xlsm files (old Excel files
with macro support).

We could keep using the old version of this dependency, but hopefully
this niche version of an ancient file format is obscure enough that
no-one is using it, and we can drop support, keeping our dependencies
up to date.

requirements.txt

@@ -222,7 +222,7 @@ wtforms==3.0.1
     # via
     #   -r requirements.in
     #   flask-wtf
-xlrd==1.2.0
+xlrd==2.0.1
     # via pyexcel-xls
 xlwt==1.3.0
     # via pyexcel-xls

tests/app/main/views/test_send.py

@@ -300,8 +300,8 @@ def test_set_sender_redirects_if_one_sms_sender(
 
 
 def test_that_test_files_exist():
-    assert len(test_spreadsheet_files) == 8
-    assert len(test_non_spreadsheet_files) == 6
+    assert len(test_spreadsheet_files) == 7
+    assert len(test_non_spreadsheet_files) == 7
 
 
 def test_should_not_allow_files_to_be_uploaded_without_the_correct_permission(