roachtest: backup-restore/mixed-version failed

**Note:** This build has runtime assertions enabled. If the same failure was hit in a run without assertions enabled, there should be a similar failure without this message. If there isn't one, then this failure is likely due to an assertion violation or (assertion) timeout.

roachtest.backup-restore/mixed-version [failed](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_RoachtestNightlyGceBazel/21347185?buildTab=log) with [artifacts](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_RoachtestNightlyGceBazel/21347185?buildTab=artifacts#/backup-restore/mixed-version) on release-26.1 @ [2f01471f35d7d7e69d8f4c8d157d66725345f5b1](https://github.com/cockroachdb/cockroach/commits/2f01471f35d7d7e69d8f4c8d157d66725345f5b1):

Failed with:

```
(mixedversion.go:893).Run: preparing to run step 28: failed to get cluster version for node 3 (system): pq: query execution canceled
test artifacts and logs in: /artifacts/backup-restore/mixed-version/run_1
```
Cluster Node to Ip Mapping:
| Node | Public IP | Private IP |
| --- | --- | --- |
| teamcity-21347185-1778739475-16-n5cpu4-0001 | 34.148.51.109 | 10.142.2.63 |
| teamcity-21347185-1778739475-16-n5cpu4-0002 | 34.23.209.23 | 10.142.2.64 |
| teamcity-21347185-1778739475-16-n5cpu4-0003 | 35.231.175.184 | 10.142.2.65 |
| teamcity-21347185-1778739475-16-n5cpu4-0004 | 34.148.46.65 | 10.142.2.66 |
| teamcity-21347185-1778739475-16-n5cpu4-0005 | 35.231.121.5 | 10.142.1.170 |

Parameters:
- arch=amd64
- cloud=gce
- coverageBuild=false
- cpu=4
- diskCount=0
- encrypted=true
- fs=ext4
- localSSD=true
- mvtDeploymentMode=separate-process
- mvtVersions=v25.1.10 → v25.2.18 → v25.3.7 → v25.4.10 → v26.1.5-dev-2f01471f35d7d7e69d8f4c8d157d66725345f5b1 (release-26.1)
- runtimeAssertionsBuild=true
Help

See: [roachtest README](https://github.com/cockroachdb/cockroach/blob/master/pkg/cmd/roachtest/README.md)

See: [How To Investigate \(internal\)](https://cockroachlabs.atlassian.net/l/c/SSSBr8c7)

See: [Grafana](https://go.crdb.dev/roachtest-grafana/teamcity-21347185/backup-restore-mixed-version/1778739706008/1778740428067)

Same failure on other branches

- #170244 roachtest: backup-restore/mixed-version failed [A-disaster-recovery C-test-failure O-roachtest O-robot T-disaster-recovery branch-release-25.2 release-blocker]
- #169309 roachtest: backup-restore/mixed-version failed [A-disaster-recovery C-test-failure O-roachtest O-robot P-2 T-disaster-recovery autosolve branch-release-24.3]
- #168594 roachtest: backup-restore/mixed-version failed [A-disaster-recovery C-test-failure O-roachtest O-robot P-2 T-disaster-recovery branch-release-25.4]
- #157896 roachtest: backup-restore/mixed-version failed [A-disaster-recovery C-test-failure O-roachtest O-robot P-2 T-disaster-recovery branch-release-25.4.0-rc release-blocker]

/cc @cockroachdb/disaster-recovery

[This test on roachdash](https://roachdash.crdb.dev/?filter=status:open%20t:.*backup-restore/mixed-version.*&sort=title+created&display=lastcommented+project) | [Improve this report!](https://github.com/cockroachdb/cockroach/tree/master/pkg/cmd/bazci/githubpost/issues)

Jira issue: CRDB-63928