Remove double/invalid options

Author: alexcanessa

lib/_options.js

@@ -45,7 +45,7 @@ module.exports = {
             description: 'The token generated with repo access'
         },
         {
-            short: '-au',
+            short: '-U',
             name: 'api-url',
             valueType: '<url>',
             description: 'Override the GitHub API URL, allows gren to connect to a private GHE installation'
@@ -71,7 +71,7 @@ module.exports = {
             defaultValue: 'issues'
         },
         {
-            short: '-im',
+            short: '-a',
             name: 'include-messages',
             valueType: '<merge|commits|all>',
             description: 'Filter the messages added to the release notes. Only used when --data-source used is commits [commits]',
@@ -119,7 +119,7 @@ module.exports = {
             action: value => value.split(',')
         },
         {
-            short: '-mm',
+            short: '-M',
             name: 'milestone-match',
             valueType: '<prefix>',
             description: 'The title that the script needs to match to link the release to the milestone. e.g. v will match v0.1.0 [Release {{tag_name}}]',
@@ -138,7 +138,7 @@ module.exports = {
             description: 'Set the release notes as a draft.'
         },
         {
-            short: '-pr',
+            short: '-P',
             name: 'prerelease',
             description: 'Set the release as a prerelease.'
         }