Fix regex for destination namespace path

What does this MR do and why?

This fixes an error in the destination_namespace_path_regex for bulk_imports wherein the edge cases e-project-path and 1-project-path were not matching as expected.

How to set up and validate locally

1. In a terminal make a curl request to the bulk_import endpoint:

curl --location --request POST 'http://gdk.test:3000/api/v4/bulk_imports' \
--header 'Authorization: Bearer [REDACTED]' \
--header 'Content-Type: application/json' \
--data-raw '{
    "configuration": {
        "url": "http://gdk.test:3000",
        "access_token": "[REDACTED]"
    },
    "entities": [
        {
            "source_full_path": "brilliant-rainbows/high-on-a-hill",
            "source_type": "group_entity",
            "destination_slug": "carlad-gl",
            "destination_namespace": "e-project-path"
        }
    ]
}'

The api should respond with created:

{"id":167,"status":"created","source_type":"gitlab","created_at":"2023-02-28T18:15:29.097Z","updated_at":"2023-02-28T18:15:29.097Z"}%

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