UI: Reduce the visual impact of availability tags

They needn't be quite as striking since they aren't going to be the most important piece of information, at all.

The lack of spacing is somewhat concerning, but I have a separate PR in the works to alleviate that.

Author: rdw-software

src/components/API/styles.module.css

@@ -130,11 +130,9 @@ body {
 }
 
 .sinceBlock {
-  display: inline-block;
-  margin-bottom: 0.5rem;
-  font-size: 0.8rem;
-  border: 3px solid black;
+  border: 1px solid var(--ifm-color-primary-darkest);
   border-radius: 15px;
-  padding: 0.25rem 0.5rem;
-  font-weight: bold;
+  padding: 0.25rem 0.75rem;
+  font-style: oblique;
+  font-size: 0.75rem;
 }