Resolve #3435248 "Inconsistency between generalsettings.results"

Closes #3435248. Excises general_settings.pagesize in favour of general_settings.results, since the latter is already in the module schema.

config/schema/funnelback.schema.yml

+funnelback.settings:
+  type: config_object
+  label: 'Funnelback settings'
+  mapping:
+    general_settings:
+      type: mapping
+      label: 'General settings'
+      mapping:
+        collection:
+          type: string
+          label: 'Collection Name'
+        profile:
+          type: string
+          label: 'Profile Name'
+        custom_template:
+          type: string
+          label: 'Custom template'
+        base_url:
+          type: string
+          label: 'Base URL'
+        no_result_text:
+          type: string
+          label: 'No results text'
+        debug_mode:
+          type: string
+          label: 'Debug mode'
+        results:
+          type: integer
+          label: 'Number of results'
+    autocomplete:
+      type: mapping
+      label: 'Autocomplete settings'
+      mapping:
+        enabled:
+          type: boolean
+          label: 'Autocomplete enabled'
+        results:
+          type: integer
+          label: 'Number of autocomplete suggestions'
+    display_mode:
+      type: mapping
+      label: 'Display mode settings'
+      mapping:
+        enabled:
+          type: boolean
+          label: 'Display mode enabled'
+        id:
+          type: string
+          label: 'Display mode ID'