Update README_en.md

Author: UlricQin

README_en.md

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 ## What is Nightingale
 
-Nightingale is an open-source project focused on alerting. Similar to Grafana's data source integration approach, Nightingale also connects with various existing data sources. However, while Grafana focuses on visualization, Nightingale focuses alerting engines.
+Nightingale is an open-source project focused on alerting. Similar to Grafana's data source integration approach, Nightingale also connects with various existing data sources. However, while Grafana focuses on visualization, Nightingale focuses on alerting engines.
 
 Originally developed and open-sourced by Didi, Nightingale was donated to the China Computer Federation Open Source Development Committee (CCF ODC) on May 11, 2022, becoming the first open-source project accepted by the CCF ODC after its establishment.