Update README.md

spelling fix

README.md

@@ -10,7 +10,7 @@ Go to `More->Reports->Report Plugins`
 Click 'Upload a plugin' and browse to the kpz file downloaded from the release page
 
 To use:
-1. - From the plugins page click 'Run report' for the Unused Authoirty Report
+1. - From the plugins page click 'Run report' for the Unused Authority Report
 1. - Enter a range of auhtority ids (record numbers) to check, _or_ enter the creation date of the authority records.
 **Note - the plugin has a hardcoded limit of 5000 records**. It is recommended to start with smaller batches
 1. - Choose to display results as HTML or download in a CSV