Bump govuk_template_jinja to 0.18.1
Bump govuk_template_jinja to 0.18.1

https://github.com/alphagov/govuk_template/blob/master/CHANGELOG.md

Remove gov.uk prefix from relative links when printing (PR #234)
Fix a .visually-hidden bug on GOV.UK (PR #177)

nhsbsa/ppc-prototype,joelanman/govuk_prototype_kit,alphagov/govuk_prototype_kit,BucksCountyCouncil/verify-local-patterns,Demwunz/esif-prototype,davedark/proto-timeline,alphagov/govuk_prototype_kit,kenmaddison-scc/verify-local-patterns,arminio/govuk_prototype_kit,dwpdigitaltech/ejs-prototype,hannalaakso/accessible-timeout-warning,Demwunz/esif-prototype,dwpdigitaltech/ejs-prototype,chrishanes/pvb_prisoner_proto,joelanman/govuk_prototype_kit,dwpdigitaltech/hrt-prototype,gavinwye/govuk_prototype_kit,dwpdigitaltech/hrt-prototype,abbott567/govuk_prototype_kit,davedark/proto-timeline,kenmaddison-scc/verify-local-patterns,abbott567/govuk_prototype_kit,benjeffreys/hmcts-idam-proto,companieshouse/ch-accounts-prototype,DilwoarH/GDS-Prototype-DM-SavedSearch,dwpdigitaltech/ejs-prototype,DilwoarH/GDS-Prototype-DM-SavedSearch,samwake/hoddat-cofc-caseworking,benjeffreys/hmcts-idam-proto,samwake/hoddat-cofc-caseworking,samwake/hoddat-cofc-caseworking,arminio/govuk_prototype_kit,hannalaakso/accessible-timeout-warning,BucksCountyCouncil/verify-local-patterns,tsmorgan/marx,nhsbsa/ppc-prototype,paulpod/invgov,danblundell/verify-local-patterns,danblundell/verify-local-patterns,gup-dwp/pip-prototype-v2,tsmorgan/marx,BucksCountyCouncil/verify-local-patterns,karlparton/my-govuk,arminio/govuk_prototype_kit,abbott567/govuk_prototype_kit,chrishanes/pvb_prisoner_proto,karlparton/my-govuk,karlparton/my-govuk,DilwoarH/GDS-Prototype-DM-SavedSearch,kenmaddison-scc/verify-local-patterns,joelanman/govuk_prototype_kit,dwpdigitaltech/hrt-prototype,gup-dwp/pip-prototype-v2,danblundell/verify-local-patterns,gavinwye/govuk_prototype_kit,paulpod/invgov,tsmorgan/marx,davedark/proto-timeline,gup-dwp/pip-prototype-v2,alphagov/govuk_prototype_kit,companieshouse/ch-accounts-prototype,paulpod/invgov,nhsbsa/ppc-prototype,chrishanes/pvb_prisoner_proto,Demwunz/esif-prototype,hannalaakso/accessible-timeout-warning,benjeffreys/hmcts-idam-proto