Replace "text" code fence with "plaintext"

doc/administration/troubleshooting/tracing_correlation_id.md

@@ -65,7 +65,7 @@ display values we most likely care about.
 sudo gitlab-ctl tail gitlab-rails/production_json.log | jq 'select(.username == "bob") | "User: \(.username), \(.method) \(.path), \(.controller)#\(.action), ID: \(.correlation_id)"'
 ```
 
-```text
+```plaintext
 "User: bob, GET /root/linux, ProjectsController#show, ID: U7k7fh6NpW3"
 "User: bob, GET /root/linux/commits/master/signatures, Projects::CommitsController#signatures, ID: XPIHpctzEg1"
 "User: bob, GET /root/linux/blob/master/README, Projects::BlobController#show, ID: LOt9hgi1TV4"
@@ -79,7 +79,7 @@ This example uses only grep and tr, which are more likely to be installed than j
 sudo gitlab-ctl tail gitlab-rails/production_json.log | grep '"username":"bob"' | tr ',' '\n' | egrep 'method|path|correlation_id'
 ```
 
-```text
+```plaintext
 {"method":"GET"
 "path":"/root/linux"
 "username":"bob"
@@ -106,7 +106,7 @@ combo should find what you're looking for.
 find /var/log/gitlab -type f -mtime 0 -exec grep 'LOt9hgi1TV4' '{}' '+'
 ```
 
-```text
+```plaintext
 /var/log/gitlab/gitlab-workhorse/current:{"correlation_id":"LOt9hgi1TV4","duration_ms":2478,"host":"gitlab.domain.tld","level":"info","method":"GET","msg":"access","proto":"HTTP/1.1","referrer":"https://gitlab.domain.tld/root/linux","remote_addr":"68.0.116.160:0","remote_ip":"[filtered]","status":200,"system":"http","time":"2019-09-17T22:17:19Z","uri":"/root/linux/blob/master/README?format=json\u0026viewer=rich","user_agent":"Mozilla/5.0 (Mac) Gecko Firefox/69.0","written_bytes":1743}
 /var/log/gitlab/gitaly/current:{"correlation_id":"LOt9hgi1TV4","grpc.code":"OK","grpc.meta.auth_version":"v2","grpc.meta.client_name":"gitlab-web","grpc.method":"FindCommits","grpc.request.deadline":"2019-09-17T22:17:47Z","grpc.request.fullMethod":"/gitaly.CommitService/FindCommits","grpc.request.glProjectPath":"root/linux","grpc.request.glRepository":"project-1","grpc.request.repoPath":"@hashed/6b/86/6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b.git","grpc.request.repoStorage":"default","grpc.request.topLevelGroup":"@hashed","grpc.service":"gitaly.CommitService","grpc.start_time":"2019-09-17T22:17:17Z","grpc.time_ms":2319.161,"level":"info","msg":"finished streaming call with code OK","peer.address":"@","span.kind":"server","system":"grpc","time":"2019-09-17T22:17:19Z"}
 /var/log/gitlab/gitlab-rails/production_json.log:{"method":"GET","path":"/root/linux/blob/master/README","format":"json","controller":"Projects::BlobController","action":"show","status":200,"duration":2448.77,"view":0.49,"db":21.63,"time":"2019-09-17T22:17:19.800Z","params":[{"key":"viewer","value":"rich"},{"key":"namespace_id","value":"root"},{"key":"project_id","value":"linux"},{"key":"id","value":"master/README"}],"remote_ip":"[filtered]","user_id":2,"username":"bob","ua":"Mozilla/5.0 (Mac) Gecko Firefox/69.0","queue_duration":3.38,"gitaly_calls":1,"gitaly_duration":0.77,"rugged_calls":4,"rugged_duration_ms":28.74,"correlation_id":"LOt9hgi1TV4"}