Enable mutations v2 by default (#601)

<!-- The PR description should answer 2 (maybe 3) important questions:
-->

### What

Generated point mutations have been an opt-in feature for a while. Now
we advertise them in the Postgres getting started docs, it's probably
time to say they are generally available. This won't affect existing
configurations (a missing value still means "no generated mutations
please".

### How

Change the default.

changelog.md

@@ -4,6 +4,8 @@
 
 ### Added
 
+- Enabled point mutations by default for newly generated configuration.
+
 ### Changed
 
 ### Fixed

crates/configuration/src/version5/mod.rs

@@ -67,9 +67,7 @@ impl ParsedConfiguration {
             connection_settings: connection_settings::DatabaseConnectionSettings::empty(),
             metadata: metadata::Metadata::default(),
             introspection_options: options::IntrospectionOptions::default(),
-            // we'll change this to `Some(MutationsVersions::V1)` when we
-            // want to "release" this behaviour
-            mutations_version: None,
+            mutations_version: Some(metadata::mutations::MutationsVersion::V2),
         }
     }
 

crates/tests/databases-tests/src/postgres/snapshots/databases_tests__postgres__cli_version5_tests__postgres_current_only_configure_initial_configuration_is_unchanged.snap

@@ -3123,5 +3123,5 @@ expression: default_configuration
       "varchar": "string"
     }
   },
-  "mutationsVersion": null
+  "mutationsVersion": "v2"
 }