Fix YAML quotation error (#7286)

The embedded `:` was problematic, and the line also exceeded the 100
char limit. Using YAML multiline syntax addresses both issues.

Author: mhucka

docs/hardware/_index.yaml

@@ -96,7 +96,9 @@ landing_page:
       path: /cirq/hardware/pasqal/sampler
 
   - heading: Rigetti hardware
-    description: Cirq's interface with Rigetti hardware. (Note: this module was deprecated in Cirq version 1.5.)
+    description: >-
+      Cirq's interface with Rigetti hardware. (Note: this module was
+      deprecated in Cirq version 1.5.)
     options:
     - cards
     items: