Pin the version of regex to avoid error in dateparser

If you use a more recent version of regex, you get the following error:
```
  regex._regex_core.error: bad escape \d at position 7
```
Solution posted by user Mehmet Kaan Erkoç on 2022-03-16 to Stack Overflow at
<https://stackoverflow.com/a/71504213/743730>

Author: mhucka

requirements.txt

@@ -15,6 +15,13 @@ httpx                == 0.23.0
 humanize             >= 3.9.0
 python_dateutil      == 2.8.2
 pywin32              >= 301; sys_platform == 'win32'
+
+# If you use a more recent version of regex, you get the following error:
+#   "regex._regex_core.error: bad escape \d at position 7"
+# Problem analysis and solution posted by user Mehmet Kaan Erkoç on 2022-03-16
+# to Stack Overflow at https://stackoverflow.com/a/71504213/743730.
+regex                <= 2022.3.2
+
 sidetrack            >= 2.0.0
 tldextract           == 3.0.2
 validator-collection == 1.5.0