docs: add missing set_contains_any constraint docs

This constraint and affinity was added in 0.9.x but was only
documented for affinities. Close that documentation gap.

website/content/docs/job-specification/constraint.mdx

@@ -78,6 +78,7 @@ all groups (and tasks) in the job.
   distinct_property
   regexp
   set_contains
+  set_contains_any
   version
   semver
   is_set
@@ -179,6 +180,18 @@ constraint {
   }
   ```
 
+- `"set_contains_any"` - Specifies a contains constraint against the attribute. The
+  attribute and the list being checked are split using commas. This will check
+  that the given attribute contains **any** of the specified elements.
+
+  ```hcl
+  constraint {
+    attribute = "..."
+    operator  = "set_contains_any"
+    value     = "a,b,c"
+  }
+  ```
+
 - `"version"` - Specifies a version constraint against the attribute. This
   supports a comma-separated list of constraints, including the pessimistic
   operator. `version` will not consider a prerelease (eg `1.6.0-beta`)