Template params can only have one argument

The fact that a promise can also be rejected with a Throwable and/or Exception is implied and there is no need to also define that here.

Refs: reactphp/promise#223

Author: WyriHaximus

README.md

@@ -277,7 +277,7 @@ trigger at the earliest possible time in the future.
 
 ### parallel()
 
-The `parallel(iterable<callable():PromiseInterface<mixed,Exception>> $tasks): PromiseInterface<array<mixed>,Exception>` function can be used
+The `parallel(iterable<callable():PromiseInterface<mixed>> $tasks): PromiseInterface<array<mixed>>` function can be used
 like this:
 
 ```php
@@ -319,7 +319,7 @@ React\Async\parallel([
 
 ### series()
 
-The `series(iterable<callable():PromiseInterface<mixed,Exception>> $tasks): PromiseInterface<array<mixed>,Exception>` function can be used
+The `series(iterable<callable():PromiseInterface<mixed>> $tasks): PromiseInterface<array<mixed>>` function can be used
 like this:
 
 ```php
@@ -361,7 +361,7 @@ React\Async\series([
 
 ### waterfall()
 
-The `waterfall(iterable<callable(mixed=):PromiseInterface<mixed,Exception>> $tasks): PromiseInterface<mixed,Exception>` function can be used
+The `waterfall(iterable<callable(mixed=):PromiseInterface<mixed>> $tasks): PromiseInterface<mixed>` function can be used
 like this:
 
 ```php

src/functions.php

@@ -359,8 +359,8 @@ function coroutine(callable $function, ...$args): PromiseInterface
 }
 
 /**
- * @param iterable<callable():PromiseInterface<mixed,Exception>> $tasks
- * @return PromiseInterface<array<mixed>,Exception>
+ * @param iterable<callable():PromiseInterface<mixed>> $tasks
+ * @return PromiseInterface<array<mixed>>
  */
 function parallel(iterable $tasks): PromiseInterface
 {
@@ -418,8 +418,8 @@ function parallel(iterable $tasks): PromiseInterface
 }
 
 /**
- * @param iterable<callable():PromiseInterface<mixed,Exception>> $tasks
- * @return PromiseInterface<array<mixed>,Exception>
+ * @param iterable<callable():PromiseInterface<mixed>> $tasks
+ * @return PromiseInterface<array<mixed>>
  */
 function series(iterable $tasks): PromiseInterface
 {
@@ -469,8 +469,8 @@ function series(iterable $tasks): PromiseInterface
 }
 
 /**
- * @param iterable<callable(mixed=):PromiseInterface<mixed,Exception>> $tasks
- * @return PromiseInterface<mixed,Exception>
+ * @param iterable<callable(mixed=):PromiseInterface<mixed>> $tasks
+ * @return PromiseInterface<mixed>
  */
 function waterfall(iterable $tasks): PromiseInterface
 {