[docs] Fix backer alt text

docs/src/modules/components/backers.md

@@ -4,9 +4,9 @@ The core of Material-UI is a [crowd-funded](/discover-more/backers/) open-source
 
 ### Diamond 💎
 
-*3/3 slots available*
+_3/3 slots available_
 
-Diamond Sponsors are those who have pledged $2,000/month and more to Material-UI.
+Diamond Sponsors are those who have pledged \$2,000/month and more to Material-UI.
 Please contact us at [email protected] to subscribe to this tier.
 
 ### Gold 🏆
@@ -21,10 +21,10 @@ via [Patreon](https://www.patreon.com/oliviertassinari)
 via [OpenCollective](https://opencollective.com/material-ui)
 
 <p style="display: flex; justify-content: center; flex-wrap: wrap;">
-  <a data-ga-event-category="sponsors" data-ga-event-action="logo" data-ga-event-label="callemall" href="https://www.call-em-all.com" rel="noopener sponsored" target="_blank" style="margin-right: 16px;"><img src="https://images.opencollective.com/proxy/images?src=https%3A%2F%2Fopencollective-production.s3-us-west-1.amazonaws.com%2Ff4053300-e0ea-11e7-acf0-0fa7c0509f4e.png&height=100" alt="callemall" title="The easy way to message your group" width="100" loading="lazy"></a>
+  <a data-ga-event-category="sponsors" data-ga-event-action="logo" data-ga-event-label="callemall" href="https://www.call-em-all.com" rel="noopener sponsored" target="_blank" style="margin-right: 16px;"><img src="https://images.opencollective.com/proxy/images?src=https%3A%2F%2Fopencollective-production.s3-us-west-1.amazonaws.com%2Ff4053300-e0ea-11e7-acf0-0fa7c0509f4e.png&height=100" alt="call-em-all" title="The easy way to message your group" width="100" loading="lazy"></a>
 </p>
 
-Gold Sponsors are those who have pledged $500/month and more to Material-UI.
+Gold Sponsors are those who have pledged \$500/month and more to Material-UI.
 
 ### There are more!