fix test

Author: rahul2393

google-cloud-spanner/src/test/java/com/google/cloud/spanner/ChannelUsageTest.java

@@ -133,7 +133,7 @@ public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
                             Metadata.Key.of(
                                 "x-response-encoding", Metadata.ASCII_STRING_MARSHALLER)));
                     // Extract channel hint from X-Goog-Spanner-Request-Id header
-                    String requestId = headers.get(XGoogSpannerRequestId.REQUEST_HEADER_KEY);
+                    String requestId = headers.get(XGoogSpannerRequestId.REQUEST_ID_HEADER_KEY);
                     if (requestId != null) {
                       // Format:
                       // <version>.<randProcessId>.<nthClientId>.<nthChannelId>.<nthRequest>.<attempt>

google-cloud-spanner/src/test/java/com/google/cloud/spanner/RetryOnDifferentGrpcChannelMockServerTest.java

@@ -109,7 +109,7 @@ public <ReqT, RespT> Listener<ReqT> interceptCall(
             SERVER_ADDRESSES.putIfAbsent(methodName, addresses);
           }
         }
-        String requestId = metadata.get(XGoogSpannerRequestId.REQUEST_HEADER_KEY);
+        String requestId = metadata.get(XGoogSpannerRequestId.REQUEST_ID_HEADER_KEY);
         if (requestId != null) {
           // REQUEST_ID format: version.randProcessId.nthClientId.nthChannelId.nthRequest.attempt
           String[] parts = requestId.split("\\.");

google-cloud-spanner/src/test/java/com/google/cloud/spanner/TransactionChannelHintTest.java

@@ -122,7 +122,7 @@ public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
                       Metadata headers,
                       ServerCallHandler<ReqT, RespT> next) {
                     // Extract channel hint from X-Goog-Spanner-Request-Id header
-                    String requestId = headers.get(XGoogSpannerRequestId.REQUEST_HEADER_KEY);
+                    String requestId = headers.get(XGoogSpannerRequestId.REQUEST_ID_HEADER_KEY);
                     if (requestId != null) {
                       // Format:
                       // <version>.<randProcessId>.<nthClientId>.<nthChannelId>.<nthRequest>.<attempt>