ci: remove last use of DANDI_ALLOW_LOCALHOST_URLS env var

The env var DANDI_ALLOW_LOCALHOST_URLS was removed from the codebase
in a12f2e4 (2023), when the DANDI_INSTANCE_URL defaulted to localhost
and AnyHttpUrl was used unconditionally. This removes the remaining
reference in the dandi-cli test workflow, which has been a no-op since
that commit.

Closes: #67

Author: candleindark

.github/workflows/test-dandi-cli.yml

@@ -13,7 +13,6 @@ jobs:
     runs-on: ${{ matrix.os }}
     env:
       NO_ET: 1
-      DANDI_ALLOW_LOCALHOST_URLS: 1
       DANDI_TESTS_PULL_DOCKER_COMPOSE: 0
     strategy:
       fail-fast: false