Billing: Update receipts to use monospaced font in Receipt and Transaction IDs

[chrisfromthelc]

Changes proposed in this Pull Request

This PR will address concerns in 528-gh-Automattic/payments-shilling, where users or others may easily misread proportional font transaction IDs (swapping I for l for example). Changing the IDs to a monospace font should help with legibility.

Testing instructions

1. Switch to this branch.
2. Navigate to a receipt that contains a transaction ID.
3. You should see the transaction ID displayed in a monospaced font.

Before:

After:

Resolves 528-gh-Automattic/payments-shilling

[github-actions]

Link to Calypso live: https://calypso.live?image=registry.a8c.com/calypso/app:commit-6d96210d7c137cf5bed1641326a162a350127c9a
Link to Jetpack Cloud live: https://calypso.live?image=registry.a8c.com/calypso/app:commit-6d96210d7c137cf5bed1641326a162a350127c9a&env=jetpack
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[matticbot]

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

Sections (~9 bytes added 📈 [gzipped])

name            parsed_size           gzip_size
site-purchases        +62 B  (+0.0%)       +9 B  (+0.0%)
purchases             +62 B  (+0.0%)       +9 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.

[michaeldcain]