fix(readme): udpate example

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---

Author: hans2001

lib/node_modules/@stdlib/stats/incr/nanmgmean/README.md

@@ -127,7 +127,11 @@ accumulator = incrnanmgmean( 5 );
 
 // For each simulated datum, update the moving geometric mean...
 for ( i = 0; i < 100; i++ ) {
-    v = randu() * 100.0;
+    if ( randu() < 0.2 ) {
+        v = NaN;
+    } else {
+        v = randu() * 100.0;
+    }
     accumulator( v );
 }
 console.log( accumulator() );

lib/node_modules/@stdlib/stats/incr/nanmgmean/lib/main.js

@@ -60,7 +60,6 @@ var incrmgmean = require( '@stdlib/stats/incr/mgmean' );
 */
 function incrnanmgmean( W ) {
 	var acc = incrmgmean( W );
-
 	return accumulator;
 
 	/**