chore: rewrite user-facing messages in Erpnext Integrations module

Conservative cleanup of frappe.throw/msgprint messages per the message style
guide; meaning, severity, and .format() arguments are unchanged:

- index bare {} placeholders as {0}/{1}/... so translators can reorder
- move f-strings / .format() / concatenation out of _() (they break gettext
  extraction and never translate)
- wrap translatable dynamic values (DocType/Select labels) in _()
- fix grammar and colloquialisms
- drop no-op _() wrapping runtime-built strings

Part of #53976.

erpnext/erpnext_integrations/doctype/plaid_settings/plaid_settings.py

@@ -171,7 +171,7 @@ def add_bank_accounts(response: str | dict, bank: str | dict, company: str):
 			except Exception:
 				frappe.log_error("Plaid Link Error")
 				frappe.throw(
-					_("There was an error updating Bank Account {} while linking with Plaid.").format(
+					_("There was an error updating Bank Account {0} while linking with Plaid.").format(
 						existing_bank_account
 					),
 					title=_("Plaid Link Failed"),