document OTEL_PHP_DEBUG_SCOPES_DISABLED

[CRC-Mismatch]

This setting is currently documented only under a specific description for the Context:

opentelemetry.io/content/en/docs/languages/php/context.md

Lines 141 to 143 in 471c572

	If you understand why `DebugScope` is complaining and accept the risks, then you
	can disable the feature entirely by setting `OTEL_PHP_DEBUG_SCOPES_DISABLED` to
	a truthy value.

[theletterf]

@open-telemetry/php-approvers Please have a look, thanks!

[theletterf]

/fix:format

[opentelemetrybot]

You triggered fix:format action run at https://github.com/open-telemetry/opentelemetry.io/actions/runs/9990660522