fix: set missing default type value

Author: kgryte

lib/node_modules/@stdlib/utils/count-by/docs/types/index.d.ts

@@ -102,7 +102,7 @@ interface Results<T> {
 * var out = countBy( arr, indicator );
 * // returns { 'b': 3, 'f': 1 }
 */
-declare function countBy<T>( collection: Collection<T>, indicator: Indicator<T> ): Results<T>;
+declare function countBy<T = unknown>( collection: Collection<T>, indicator: Indicator<T> ): Results<T>;
 
 /**
 * Groups values according to an indicator function and returns group counts.
@@ -133,7 +133,7 @@ declare function countBy<T>( collection: Collection<T>, indicator: Indicator<T>
 * var out = countBy( arr, indicator );
 * // returns { 'b': 3, 'f': 1 }
 */
-declare function countBy<T>( collection: Collection<T>, options: Options<T>, indicator: Indicator<T> ): Results<T>;
+declare function countBy<T = unknown>( collection: Collection<T>, options: Options<T>, indicator: Indicator<T> ): Results<T>;
 
 
 // EXPORTS //