[Concurrency] Remove symbols of startSynchronously, make it AEIC

In preparation for removal. This spelling of Task.immediate was before
SE-review and was NOT accepted and therefore we should try to remove it
entirely.

Author: ktoso

stdlib/public/Concurrency/Task+immediate.swift.gyb

@@ -33,17 +33,10 @@ import Swift
 @available(SwiftStdlib 6.2, *)
 extension Task where Failure == ${FAILURE_TYPE} {
 
-  // FIXME: This method is left in place to give adopters time to switch to `immediate` but it's going
-  // to be removed soon, since this spelling was rejected as part of SE-0472 proposal.
   @available(SwiftStdlib 6.2, *)
-  @available(*, deprecated, renamed: "immediate")
-  // Used to preserve the symbols as originally declared without `@isolated(any)` attribute on `operation:`.
-  % if FAILURE_TYPE == "Error":
-  @_silgen_name("$sScTss5Error_pRs_rlE18startSynchronously4name8priority_ScTyxsAA_pGSSSg_ScPSgxyYaKcntFZ")
-  % elif FAILURE_TYPE == "Never":
-  @_silgen_name("$sScTss5NeverORs_rlE18startSynchronously4name8priority_ScTyxABGSSSg_ScPSgxyYaKcntFZ")
-  % end
+  @available(*, deprecated, message: "Deprecated spelling of Task.immediate. This method will be removed.")
   @discardableResult
+  @_alwaysEmitIntoClient // moved to AEIC in order to eventually remove this function.
   public static func startSynchronously(
     name: String? = nil,
     priority: TaskPriority? = nil,