Fix typo in installation.md
Fix typo in installation.md

specificed -> specified
influxdata/docs.influxdata.com,Tomcat-Engineering/docs.influxdata.com,influxdata/docs.influxdata.com,Tomcat-Engineering/docs.influxdata.com,influxdb/docs.influxdata.com,influxdata/docs.influxdata.com,influxdata/docs.influxdata.com,influxdata/docs.influxdata.com,influxdb/docs.influxdata.com,Tomcat-Engineering/docs.influxdata.com,influxdb/docs.influxdata.com