Update the validator in multivpc module (GoogleCloudPlatform#5156)

Author: SwarnaBharathiMantena

modules/network/multivpc/README.md

@@ -2,7 +2,7 @@
 
 This module accomplishes the following:
 
-* Creates 2 to 8 [VPC networks][vpc]
+* Creates 1 to 8 [VPC networks][vpc]
   * Each VPC contains exactly 1 subnetwork
   * Each subnetwork contains distinct IP address ranges
 * Outputs the `additional_networks` parameter, which is compatible with Slurm

modules/network/multivpc/metadata.yaml

@@ -22,6 +22,6 @@ ghpc:
   - validator: range
     inputs:
       vars: [network_count]
-      min: 2
+      min: 1
       max: 8
-    error_message: "The 'network_count' must be between 2 and 8. Use the standard Toolkit module at 'modules/network/vpc' for count = 1."
+    error_message: "The 'network_count' must be between 1 and 8."