update the error message of OOM (#15735) (#15756)

Author: ti-chi-bot

troubleshoot-tidb-oom.md

@@ -19,7 +19,7 @@ The following are some typical OOM phenomena:
     - **TiDB-Runtime** > **Memory Usage** shows that the `estimate-inuse` metric keeps rising.
 
 - Check `tidb.log`, and you can find the following log entries:
-    - An alarm about OOM: `[WARN] [memory_usage_alarm.go:139] ["tidb-server has the risk of OOM. Running SQLs and heap profile will be recorded in record path"]`. For more information, see [`memory-usage-alarm-ratio`](/system-variables.md#tidb_memory_usage_alarm_ratio).
+    - An alarm about OOM: `[WARN] [memory_usage_alarm.go:139] ["tidb-server has the risk of OOM because of memory usage exceeds alarm ratio. Running SQLs and heap profile will be recorded in record path"]`. For more information, see [`memory-usage-alarm-ratio`](/system-variables.md#tidb_memory_usage_alarm_ratio).
     - A log entry about restart: `[INFO] [printer.go:33] ["Welcome to TiDB."]`.
 
 ## Overall troubleshooting process
@@ -189,7 +189,7 @@ To locate the root cause of an OOM issue, you need to collect the following info
 - Run `grep "tidb-server has the risk of OOM" tidb.log` to check the path of the alert file collected by TiDB Server. The following is an example output:
 
     ```shell
-    ["tidb-server has the risk of OOM. Running SQLs and heap profile will be recorded in record path"] ["is tidb_server_memory_limit set"=false] ["system memory total"=14388137984] ["system memory usage"=11897434112] ["tidb-server memory usage"=11223572312] [memory-usage-alarm-ratio=0.8] ["record path"="/tmp/0_tidb/MC4wLjAuMDo0MDAwLzAuMC4wLjA6MTAwODA=/tmp-storage/record"]
+    ["tidb-server has the risk of OOM because of memory usage exceeds alarm ratio. Running SQLs and heap profile will be recorded in record path"] ["is tidb_server_memory_limit set"=false] ["system memory total"=14388137984] ["system memory usage"=11897434112] ["tidb-server memory usage"=11223572312] [memory-usage-alarm-ratio=0.8] ["record path"="/tmp/0_tidb/MC4wLjAuMDo0MDAwLzAuMC4wLjA6MTAwODA=/tmp-storage/record"]
     ```
 
 ## See also