fix: Add additional validation for timeout while retrieving headers

[paul1r]

What this PR does / why we need it:
Go 1.23 changed the type of error being returned in the case of a timeout while waiting for headers, as documented in this issue
Which issue(s) this PR fixes:
Fixes #14206

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• For Helm chart changes bump the Helm chart version in production/helm/loki/Chart.yaml and update production/helm/loki/CHANGELOG.md and production/helm/loki/README.md. Example PR
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

[paul1r]

progers@Pauls-MacBook-Pro gcp % /usr/local/go/bin/go version            
go version go1.22.7 darwin/arm64
progers@Pauls-MacBook-Pro gcp % /usr/local/go/bin/go test -count=1 ./...
ok  	github.com/grafana/loki/v3/pkg/storage/chunk/client/gcp	1.747s

progers@Pauls-MacBook-Pro gcp % go version
go version go1.23.1 darwin/arm64
progers@Pauls-MacBook-Pro gcp % go test -count=1 ./...
ok  	github.com/grafana/loki/v3/pkg/storage/chunk/client/gcp	1.751s

[ashwanthgoli]

LGTM