Bump Werkzeug to version 2.0.2

This is the newest version.

Pyup is complaining about vulnerabilities in version 1.0.1, specifically
> Werkzeug version 2.0.2 improves the security of the debugger cookies.
> "SameSite" attribute is set to "Strict" instead of "None", and the
> secure flag is added when on HTTPS.

Previously we were using whatever version of Werkzeug that Flask
specified this pins it to get rid of the vulnerability without having to
upgrade everything at once.

We’ve done this for the admin app already:
https://github.com/alphagov/notifications-admin/pull/4042/files

I suspect the memory usage issues we saw with version 2.0.0 have been
fixed in 2.0.2, per this line in the changelog:
> Fix memory usage for locals when using Python 3.6 or pre 0.4.17 greenlet versions.
> https://github.com/pallets/werkzeug/pull/2212

— https://werkzeug.palletsprojects.com/en/2.0.x/changes/

requirements-app.txt

@@ -25,9 +25,7 @@ rfc3987==1.3.8
 cachetools==4.2.1
 beautifulsoup4==4.9.3
 lxml==4.6.3
-
-# When we upgraded to 2.0.1 we noticed significantly higher memory usage on the API
-Werkzeug==1.0.1 # puyp: < 2.0.0
+Werkzeug==2.0.2
 
 # higher version causes build to fail on PaaS due to lack of Rust
 # see https://github.com/pyca/cryptography/issues/5810

requirements.txt

@@ -27,9 +27,7 @@ rfc3987==1.3.8
 cachetools==4.2.1
 beautifulsoup4==4.9.3
 lxml==4.6.3
-
-# When we upgraded to 2.0.1 we noticed significantly higher memory usage on the API
-Werkzeug==1.0.1 # puyp: < 2.0.0
+Werkzeug==2.0.2
 
 # higher version causes build to fail on PaaS due to lack of Rust
 # see https://github.com/pyca/cryptography/issues/5810