Fix comments in AggregateException.GetBaseException() (#107743)

* Fix comments in AggregateException.GetBaseException()

The public <summary> incorrectly stated that the method returned an AggregateException.

* Update src/libraries/System.Private.CoreLib/src/System/AggregateException.cs

Co-authored-by: Stephen Toub <[email protected]>

* Extract GetBaseException() <summary> content to <remarks>

* Update src/libraries/System.Private.CoreLib/src/System/AggregateException.cs

---------

Co-authored-by: Stephen Toub <[email protected]>
Co-authored-by: Dan Moseley <[email protected]>

Author: 3 people

src/libraries/System.Private.CoreLib/src/System/AggregateException.cs

@@ -213,13 +213,16 @@ public override void GetObjectData(SerializationInfo info, StreamingContext cont
         }
 
         /// <summary>
-        /// Returns the <see cref="AggregateException"/> that is the root cause of this exception.
+        /// Returns the <see cref="Exception"/> that is the root cause of this exception.
         /// </summary>
+        /// <remarks>
+        /// This will either be the root exception, or the first <see cref="AggregateException"/>
+        /// that contains either multiple inner exceptions or no inner exceptions at all.
+        /// </remarks>
         public override Exception GetBaseException()
         {
-            // Returns the first inner AggregateException that contains more or less than one inner exception
-
-            // Recursively traverse the inner exceptions as long as the inner exception of type AggregateException and has only one inner exception
+            // Recursively traverse the inner exceptions as long as the inner exception is of type
+            // AggregateException and has exactly one inner exception
             Exception? back = this;
             AggregateException? backAsAggregate = this;
             while (backAsAggregate != null && backAsAggregate.InnerExceptions.Count == 1)