Domains: Update TXT record error to be clearer

[eltongo]

Changes proposed in this Pull Request

This PR updates the error shown when a user tries to enter a TXT record that is longer than 255 characters.

Testing instructions

Try to add a TXT record with a value longer than 255 characters to your domain. You should see the following error:

You should see a similar error as well when the TXT record is empty.

[matticbot]

Test live: https://calypso.live/?branch=update/txt-record-length-error

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~108 bytes added 📈 [gzipped])

name     parsed_size           gzip_size
domains       +200 B  (+0.0%)     +108 B  (+0.0%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[a8ci18n]

This Pull Request is now available for translation here: https://translate.wordpress.com/deliverables/3695673

Thank you @eltongo for including a screenshot in the description! This is really helpful for our translators.

[a8ci18n]

Translation for this Pull Request has now been finished.