updated prometheus test to account for random attribute ordering

Author: bryce-b

Tests/ExportersTests/Prometheus/PrometheusExporterTests.swift

@@ -119,7 +119,8 @@ class PrometheusExporterTests: XCTestCase {
 
     // Validate measure.
     XCTAssert(responseText.contains("# TYPE testGauge gauge"))
-    XCTAssert(responseText.contains("testGauge{dim2=\"value1\",dim1=\"value1\"} 500"))
+    XCTAssert(responseText.contains("testGauge{dim2=\"value1\",dim1=\"value1\"} 500") ||
+              "testGauge{dim1=\"value1\",dim2=\"value1\"} 500"))
 
     // Validate histogram.
     XCTAssert(responseText.contains("# TYPE testHistogram histogram"))