chore: update nightly upgrade to cardano-node 10.5.3 (#3232)

Bump the nightly upgrade test environment to use cardano-node 10.5.3
instead of 10.5.1. Also update nightly system test documentation to
remove references to legacy and mixed network topologies, as legacy
topology is no longer supported in latest master.

Author: mkoura

.github/env_nightly_upgrade

@@ -1,2 +1,2 @@
-BASE_TAR_URL=https://github.com/IntersectMBO/cardano-node/releases/download/10.5.1/cardano-node-10.5.1-linux.tar.gz
+BASE_TAR_URL=https://github.com/IntersectMBO/cardano-node/releases/download/10.5.3/cardano-node-10.5.3-linux.tar.gz
 CI_BYRON_CLUSTER=true

src_docs/source/test_results/nightly_system_tests.rst

@@ -49,16 +49,13 @@ Nightly upgrade testing
    * network in Conway era
    * protocol version 10
    * Constitutional Commitee has 5 members
-   * legacy network topology
    * smoke tests
    * governance info action test
 * `Step 2 <https://cardano-tests-reports-3-74-115-22.nip.io/cardano-node-tests-nightly-upgrade/step2/>`__:  |nightly-upgrade-step2-badge|
    * upgrade all nodes except one to the latest cardano-node master
-   * mixed network topology (half nodes P2P, half nodes legacy topology)
    * smoke tests
 * `Step 3 <https://cardano-tests-reports-3-74-115-22.nip.io/cardano-node-tests-nightly-upgrade/step3/>`__:  |nightly-upgrade-step3-badge|
    * upgrade the last remaining node to latest cardano-node master
-   * P2P network topology
    * smoke tests
    * governance treasury withdrawal action test