Update multitenant version in update script (#669)

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

We automatically open `ndc-postgres-multitenant` PRs, let's make sure we
update the right part of the `Cargo.toml` file

Author: danieljharvey

.github/workflows/update-multitenant-dep.yaml

@@ -53,7 +53,7 @@ jobs:
           # there will be multiple `ndc-postgres` deps, so we target a specific
           # one, presumably the latest version. This will need updating as we
           # add new `ndc-postgres` versions into `ndc-postgres-multitenant`
-          LATEST_NDC_POSTGRES_VERSION="1"
+          LATEST_NDC_POSTGRES_VERSION="2"
 
           # Update the hash for ndc-postgres
           sed -i -e "/ndc-postgres_v${LATEST_NDC_POSTGRES_VERSION}/s/rev[ ]*=[ ]*\"[[:alnum:]]*\"/rev = \"$LATEST_SHA\"/g" $DEP_FILEPATH