SetMeterProvider panics if two connections are open

[blkt]

Describe the issue
Dependabot opened the following PR upgrading several opentelemetry dependencies in an open source project I'm maintaining.
Accepting the change causes panics for some reasons that are unclear to me, but that I managed to reproduce in a simpler script here.

Here's the list of upgrades.

Package	From	To
go.opentelemetry.io/otel/exporters/prometheus	0.51.0	0.52.0
go.opentelemetry.io/otel/exporters/stdout/stdouttrace	1.29.0	1.30.0
go.opentelemetry.io/otel/sdk	1.29.0	1.30.0
go.opentelemetry.io/otel/sdk/metric	1.29.0	1.30.0
go.opentelemetry.io/otel/trace	1.29.0	1.30.0
go.opentelemetry.io/otel/metric	1.29.0	1.30.0

I am opening the issue in this project because it only manifests with this tracing library, and splunk-otel-go version 1.19.0 with otel libraries at version 1.29.0 did not manifest this behavior.

Steps to reproduce the issue:
Use https://github.com/blkt/panicrepro to reproduce.
Branch main panics.
Branch working-version does not panic.

Attempted solutions and workarounds
No workarounds were attempted.

Expected behavior
Opening two connections should not cause any sort of panic.

Environment
Complete the following information:

• OS version: macOS 14.6.1
• Go version: 1.23.1
• splunk-otel-go version: 1.20.0

[MrAlias]

This looks related to open-telemetry/opentelemetry-go#5827