fix(i18n): correct article usage in dso-selector placeholder (fixes #5528)

(cherry picked from commit fc6057c)

Author: MukundaKatta

src/assets/i18n/en.json5

@@ -1747,7 +1747,7 @@
 
   "dso-selector.no-results": "No {{ type }} found",
 
-  "dso-selector.placeholder": "Search for a {{ type }}",
+  "dso-selector.placeholder": "Search for {{ type }}",
 
   "dso-selector.placeholder.type.community": "community",
 
@@ -4335,7 +4335,7 @@
 
   "resource-policies.form.eperson-group-list.select.btn": "Select",
 
-  "resource-policies.form.eperson-group-list.tab.eperson": "Search for a ePerson",
+  "resource-policies.form.eperson-group-list.tab.eperson": "Search for an ePerson",
 
   "resource-policies.form.eperson-group-list.tab.group": "Search for a group",