Explicit ipv4 address for locally-running test Astra DB+hcd

[sl-at-ibm]

It seems that if the interface admits ipv6, calling the URL "localhost" resolves to ipv6, preventing the integration testing to run against a local Data API + HCD. On my system this is what I see:

$> scripts/test.ts -f 'integration.'  -local


Running prelude.test.ts
  1) "before all" hook in "{root}"                                                                              

  0 passing (9ms)
  1 failing

  1) "before all" hook in "{root}":
     Error: connect ECONNREFUSED ::1:8181
      at __node_internal_captureLargerStackTrace (node:internal/errors:496:5)
      at __node_internal_exceptionWithHostPort (node:internal/errors:671:12)
      at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1555:16)
      at TCPConnectWrap.callbackTrampoline (node:internal/async_hooks:128:17)

This PR simply uses the explicit format for an ipv4 address. And indeed I can run integration tests.

With this change, the ITs start all right:

$> scripts/test.ts -f 'integration.'  -local


Running prelude.test.ts
creating keyspace 'other_keyspace'
  (ASTRA) integration.administration.astra-admin                                                                
    - should not stop you from creating an AstraAdmin without a token
    findAvailableRegions
      - should work

  integration.administration.db-admin
    ✔ (LONG) works (2236ms)
    ✔ should findEmbeddingProviders
    - (ASTRA) should timeout

[etc, etc...]

(also in the .env one should prefer this notation, I think - but that file is gitignored and I think if not defined the scripts/test.ts is the default).

Note: I should have ipv6 enabled indeed:

$> ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host noprefixroute 
       valid_lft forever preferred_lft forever