chore: introduce more deprecated things

lib/EmitterInterface.php

@@ -47,7 +47,7 @@ public function once(string $eventName, callable $callBack, int $priority = 100)
      * Lastly, if there are 5 event handlers for an event. The continueCallback
      * will be called at most 4 times.
      */
-    public function emit(string $eventName, array $arguments = [], ?callable $continueCallBack = null): bool;
+    public function emit(string $eventName, array $arguments = [], callable $continueCallBack = null): bool;
 
     /**
      * Returns the list of listeners for an event.

lib/EmitterTrait.php

@@ -73,7 +73,7 @@ public function once(string $eventName, callable $callBack, int $priority = 100)
      * Lastly, if there are 5 event handlers for an event. The continueCallback
      * will be called at most 4 times.
      */
-    public function emit(string $eventName, array $arguments = [], ?callable $continueCallBack = null): bool
+    public function emit(string $eventName, array $arguments = [], callable $continueCallBack = null): bool
     {
         if (\is_null($continueCallBack)) {
             foreach ($this->listeners($eventName) as $listener) {

lib/Promise.php

@@ -58,7 +58,7 @@ class Promise
      * Each are callbacks that map to $this->fulfill and $this->reject.
      * Using the executor is optional.
      */
-    public function __construct(?callable $executor = null)
+    public function __construct(callable $executor = null)
     {
         if ($executor) {
             $executor(
@@ -87,7 +87,7 @@ public function __construct(?callable $executor = null)
      * If either of the callbacks throw an exception, the returned promise will
      * be rejected and the exception will be passed back.
      */
-    public function then(?callable $onFulfilled = null, ?callable $onRejected = null): Promise
+    public function then(callable $onFulfilled = null, callable $onRejected = null): Promise
     {
         // This new subPromise will be returned from this function, and will
         // be fulfilled with the result of the onFulfilled or onRejected event
@@ -220,7 +220,7 @@ public function wait()
      * correctly, and any chained promises are also correctly fulfilled or
      * rejected.
      */
-    private function invokeCallback(Promise $subPromise, ?callable $callBack = null)
+    private function invokeCallback(Promise $subPromise, callable $callBack = null)
     {
         // We use 'nextTick' to ensure that the event handlers are always
         // triggered outside of the calling stack in which they were originally

lib/WildcardEmitterTrait.php

@@ -82,7 +82,7 @@ public function once(string $eventName, callable $callBack, int $priority = 100)
      * Lastly, if there are 5 event handlers for an event. The continueCallback
      * will be called at most 4 times.
      */
-    public function emit(string $eventName, array $arguments = [], ?callable $continueCallBack = null): bool
+    public function emit(string $eventName, array $arguments = [], callable $continueCallBack = null): bool
     {
         if (\is_null($continueCallBack)) {
             foreach ($this->listeners($eventName) as $listener) {
@@ -195,7 +195,7 @@ public function removeListener(string $eventName, callable $listener): bool
      * removed. If it is not specified, every listener for every event is
      * removed.
      */
-    public function removeAllListeners(?string $eventName = null)
+    public function removeAllListeners(string $eventName = null)
     {
         if (\is_null($eventName)) {
             $this->listeners = [];