dont publish mergeResultCode method since is only used internally

Author: Ignacio Bonafonte

Sources/OpenTelemetrySdk/Metrics/Export/MetricExporter.swift

@@ -22,7 +22,7 @@ public enum MetricExporterResultCode {
 
     /// Merges the current result code with other result code
     /// - Parameter newResultCode: the result code to merge with
-    public mutating func mergeResultCode(newResultCode: MetricExporterResultCode) {
+    mutating func mergeResultCode(newResultCode: MetricExporterResultCode) {
         // If both results are success then return success.
         if self == .success, newResultCode == .success {
             self = .success

Sources/OpenTelemetrySdk/Trace/Export/SpanExporter.swift

@@ -43,7 +43,7 @@ public enum SpanExporterResultCode {
 
     /// Merges the current result code with other result code
     /// - Parameter newResultCode: the result code to merge with
-    public mutating func mergeResultCode(newResultCode: SpanExporterResultCode) {
+    mutating func mergeResultCode(newResultCode: SpanExporterResultCode) {
         // If both results are success then return success.
         if self == .success && newResultCode == .success {
             self = .success