Make style to remove diagram border more reusable (#122)

Ideally we'd be using classes here, but we'd need to install
something like the Eleventy image plugin to make that work.

Instead we use a common, descriptive filename suffix to avoid
building up a list of individual images in the CSS file.

Author: mikejamesthompson

…-mavis/mavis-record-flow-nhs-numbers.png …s/nhs-number-flow-borderless-diagram.pngapp/images/manage-vaccinations-in-schools/2025/05/improving-coverage-of-nhs-numbers-in-mavis/mavis-record-flow-nhs-numbers.png renamed to app/images/manage-vaccinations-in-schools/2025/05/improving-coverage-of-nhs-numbers-in-mavis/nhs-number-flow-borderless-diagram.png app/images/manage-vaccinations-in-schools/2025/05/improving-coverage-of-nhs-numbers-in-mavis/mavis-record-flow-nhs-numbers.png renamed to app/images/manage-vaccinations-in-schools/2025/05/improving-coverage-of-nhs-numbers-in-mavis/nhs-number-flow-borderless-diagram.png

@@ -13,7 +13,7 @@ As of Friday 2nd May 2025, across all SAIS teams using Mavis, there were around
 
 Our most recently onboarded SAIS provider experienced 10% of records having no NHS number after uploading and automatic matching in Mavis. Our first SAIS provider also had 10% of records without NHS numbers after uploading to Mavis. They have since reduced this to less than 1% through manual matching of records.
 
-![A diagram showing the flow of patient records into Mavis.](./mavis-record-flow-nhs-numbers.png "**Figure 1:** A diagram showing the flow of patient records into Mavis.")
+![A diagram showing the flow of patient records into Mavis.](./nhs-number-flow-borderless-diagram.png "**Figure 1:** A diagram showing the flow of patient records into Mavis.")
 
 ### Sources of records
 

app/posts/manage-vaccinations-in-schools/2025/05/improving-coverage-of-nhs-numbers-in-mavis.md

@@ -60,7 +60,7 @@ $govuk-font-family: Frutiger W01, arial, sans-serif;
 
   // Improve display of mission patch images inside figures
   figure:has(img[src$="mission-patch.png"]),
-  figure:has(img[src$="mavis-record-flow-nhs-numbers.png"]) {
+  figure:has(img[src$="borderless-diagram.png"]) {
     background-color: transparent;
     border: 0;