Fix English 'a[n]' grammar (see issue go-gitea#3512).

options/locale/locale_en-US.ini

@@ -249,7 +249,7 @@ Content = Content
 require_error = ` cannot be empty.`
 alpha_dash_error = ` must be valid alphanumeric or dash(-_) characters.`
 alpha_dash_dot_error = ` must be valid alphanumeric, dash(-_) or dot characters.`
-git_ref_name_error = ` must be well formed git reference name.`
+git_ref_name_error = ` must be a well formed git reference name.`
 size_error = ` must be size %s.`
 min_size_error = ` must contain at least %s characters.`
 max_size_error = ` must contain at most %s characters.`
@@ -335,7 +335,7 @@ enable_custom_avatar = Use Custom Avatar
 choose_new_avatar = Choose new avatar
 update_avatar = Update Avatar Setting
 delete_current_avatar = Delete Current Avatar
-uploaded_avatar_not_a_image = Uploaded file is not a image.
+uploaded_avatar_not_a_image = Uploaded file is not an image.
 update_avatar_success = Your avatar setting has been updated.
 
 change_password = Change Password
@@ -914,7 +914,7 @@ settings.convert_confirm = Confirm Conversion
 settings.convert_succeed = Repository has been converted to a regular repository.
 settings.transfer = Transfer Ownership
 settings.transfer_desc = Transfer this repository to another user or to an organization in which you have admin rights.
-settings.transfer_notices_1 = - You will lose access if the new owner is a individual user.
+settings.transfer_notices_1 = - You will lose access if the new owner is an individual user.
 settings.transfer_notices_2 = - You will preserve access if the new owner is an organization and if you're one of the owners.
 settings.transfer_form_title = Please enter the following information to confirm your operation:
 settings.wiki_delete = Erase Wiki Data