Rename Pro Metrics 'Total requests made this week' report label

'Total requests made this week' wasn't a good description of the
reported data. 'Estimated total number of Pro requests' is clearer.

Also changes the data key from `:total_new_requests` to
`:estimated_total_pro_requests`

app/views/alaveteli_pro/metrics_mailer/weekly_report.text.erb

@@ -51,4 +51,4 @@
 
 <%= _('New Pro requests this week:') %> <%= @data[:new_pro_requests] %>
 
-<%= _('Total requests made this week:') %> <%= @data[:total_new_requests] %>
+<%= _('Estimated total number of Pro requests:') %> <%= @data[:estimated_total_pro_requests] %>

lib/alaveteli_pro/metrics_report.rb

@@ -20,7 +20,7 @@ def report_data
       data =
         {
           new_pro_requests: number_of_requests_created_this_week,
-          total_new_requests: estimated_number_of_pro_requests,
+          estimated_total_pro_requests: estimated_number_of_pro_requests,
           new_batches: number_of_batch_requests_created_this_week,
           new_signups: number_of_pro_signups_this_week,
           total_accounts: total_number_of_pro_accounts,

spec/lib/alaveteli_pro/metrics_report_spec.rb

@@ -65,8 +65,8 @@
       expect(subject[:new_pro_requests]).to eq 4
     end
 
-    it 'returns the total number of Pro requests' do
-      expect(subject[:total_new_requests]).to eq 5
+    it 'returns the estimated (total) number of Pro requests' do
+      expect(subject[:estimated_total_pro_requests]).to eq 5
     end
 
     it 'returns the number of batch requests' do

spec/mailers/previews/alaveteli_pro/metrics_mailer_preview.rb

@@ -6,7 +6,7 @@ def weekly_report
       data =
         {
           new_pro_requests: 104,
-          total_new_requests: 37535,
+          estimated_total_pro_requests: 37535,
           new_batches: 3,
           new_signups: 5,
           total_accounts: 284,