Update lakeflow template project_name validation message (#3856)

## Changes
Updated to align with the pattern
## Why

Why not change the pattern to allow uppercase? It is lowercase because
this name is used for certain Python modules and functions. So we'd need
to accept that we're breaking the Python conventions if we allow upper
case

## Tests
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Author: ilyakuz-db

libs/template/templates/lakeflow-pipelines/databricks_template_schema.json

@@ -17,7 +17,7 @@
             "description": "\nUnique name for this project",
             "order": 1,
             "pattern": "^[a-z0-9_]+$",
-            "pattern_match_failure_message": "Name must consist of letters, numbers, and underscores."
+            "pattern_match_failure_message": "Name must consist of lower case letters, numbers, and underscores."
         },
         "project_name_short": {
             "//": "This is a derived property based on project_name (it replaces lakeflow_project with lakeflow and strips _project|_app|_service)",