Removed tunable attribute from CTS_BUF_LIST

Signed-off-by: Jeff Ng <[email protected]>

Author: jeffng-or

flow/scripts/variables.yaml

@@ -776,8 +776,6 @@ CTS_BUF_LIST:
     List of cells used to construct the clock tree. Overrides buffer inference.
   stages:
     - cts
-  tunable: 1
-  type: float
 CTS_CLUSTER_DIAMETER:
   description: >
     Maximum diameter (in microns) of sink cluster.