use specific version of data-collect-protocol (#15)

diff --git a/.gitmodules b/.gitmodules
index 69d308e..2ded8e3 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,4 @@
 [submodule "skywalking-data-collect-protocol"]
 	path = skywalking-data-collect-protocol
 	url = https://github.com/apache/skywalking-data-collect-protocol.git
+	branch = v8.9.1
diff --git a/e2e/data/expected_context.yaml b/e2e/data/expected_context.yaml
index 288527e..5a6570d 100644
--- a/e2e/data/expected_context.yaml
+++ b/e2e/data/expected_context.yaml
@@ -23,7 +23,6 @@
     - componentId: 11000
       endTime: gt 0
       isError: false
-      operationId: 0
       operationName: /pong
       parentSpanId: 1
       peer: consumer:8082
@@ -35,7 +34,6 @@
     - componentId: 11000
       endTime: gt 0
       isError: false
-      operationId: 0
       operationName: /ping
       parentSpanId: 0
       peer: ''
@@ -52,7 +50,6 @@
     - componentId: 11000
       endTime: gt 0
       isError: false
-      operationId: 0
       operationName: /pong
       parentSpanId: 0
       peer: ''