Update api.md

need to make the reference relative as it gets deployed differently in github (top of the path is /guide/ - which could have been added, but is slightly less portable if this is moved to another provider)

content/en/docs/Developer/api.md

@@ -5,4 +5,4 @@ weight = 1
 description = "Reference for the Polaris API"
 +++
 
-{{< swaggerui src="/openapi/openapi.yaml" >}}
+{{< swaggerui src="../../../openapi/openapi.yaml" >}}