stack: improve wording

Co-authored-by: Brian Flad <bflad417@gmail.com>

internal/plans/deferring/deferred.go

@@ -440,5 +440,5 @@ func (d *Deferred) ReportModuleExpansionDeferred(addr addrs.PartialExpandedModul
 // UnexpectedProviderDeferralDiagnostic is a diagnostic that indicates that a
 // provider was deferred although deferrals were not allowed.
 func UnexpectedProviderDeferralDiagnostic(addrs addrs.AbsResourceInstance) tfdiags.Diagnostic {
-	return tfdiags.Sourceless(tfdiags.Error, "Provider deferred changes when Terraform did not allow deferrals", fmt.Sprintf("The provider signaled a deferred action for %q, but in this context deferrals are disabled. This is a bug in the provider, please file an issue.", addrs.String()))
+	return tfdiags.Sourceless(tfdiags.Error, "Provider deferred changes when Terraform did not allow deferrals", fmt.Sprintf("The provider signaled a deferred action for %q, but in this context deferrals are disabled. This is a bug in the provider, please file an issue with the provider developers.", addrs.String()))
 }