fix(notifications): rename "Created after" to "Sent out"

Based on received users' feedback, the purpose of the field seems to be
more clear this way.

Signed-off-by: Marek Libra <marek.libra@gmail.com>

.changeset/kind-steaks-flow.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-notifications': patch
+---
+
+The "Created after" filter renamed to the "Sent out" based on the received users' feedback.

plugins/notifications/src/components/NotificationsFilters/NotificationsFilters.tsx

@@ -207,12 +207,10 @@ export const NotificationsFilters = ({
 
         <Grid item xs={12}>
           <FormControl fullWidth variant="outlined" size="small">
-            <InputLabel id="notifications-filter-created">
-              Created after
-            </InputLabel>
+            <InputLabel id="notifications-filter-created">Sent out</InputLabel>
 
             <Select
-              label="Created after"
+              label="Sent out"
               labelId="notifications-filter-created"
               placeholder="Notifications since"
               value={createdAfter}