Use blocking expectation awaiting again

Tests/SwiftyHolidaysTests/Gregorian/GregorianCalculatorTests.swift

@@ -2,14 +2,6 @@ import XCTest
 @testable import SwiftyHolidays
 
 final class GregorianCalculatorTests: XCTestCase {
-    private actor Promise<Value> {
-        var value: Value?
-
-        func fulfill(with value: Value) {
-            self.value = value
-        }
-    }
-
     private let calculator = GregorianCalculator()
 
     override func setUp() {
@@ -142,7 +134,7 @@ final class GregorianCalculatorTests: XCTestCase {
         XCTAssertEqual(sema.wait(timeout: .now()), .success)
     }
 
-    func testAwaitingCalculation() async {
+    func testAwaitingCalculation() {
         let sema = DispatchSemaphore(value: 0)
         let date = HolidayDate(day: 21, month: 4, year: 2019)
         calculator.contextRef.withContext { $0.semaphores[date.year, default: [:]][.easterSunday] = sema }
@@ -152,17 +144,15 @@ final class GregorianCalculatorTests: XCTestCase {
             _ = self.calculator.easterSunday(forYear: date.year)
             awaitExpectation.fulfill()
         }
-        await fulfillment(of: [awaitExpectation], timeout: 2)
+        wait(for: [awaitExpectation], timeout: 2)
         calculator.contextRef.withContext { $0.fulfill(.easterSunday, with: date) }
         let calcExpectation = expectation(description: "Waiting for the calculator to return the calculated result")
-        let resultPromise = Promise<HolidayDate>()
-        Task.detached {
-            let calculated = self.calculator.easterSunday(forYear: date.year)
-            await resultPromise.fulfill(with: calculated)
+        var result: HolidayDate?
+        DispatchQueue.global().async {
+            result = self.calculator.easterSunday(forYear: date.year)
             calcExpectation.fulfill()
         }
-        await fulfillment(of: [calcExpectation], timeout: 2)
-        let result = await resultPromise.value
+        wait(for: [calcExpectation], timeout: 2)
         XCTAssertEqual(result, date)
     }