docs: fix C example codeblock in stats/base/dists/invgamma/mode/README.md

PR-URL: #10938

Reviewed-by: Philipp Burckhardt <pburckhardt@outlook.com>

Author: Om-A-osc

lib/node_modules/@stdlib/stats/base/dists/invgamma/mode/README.md

@@ -221,8 +221,8 @@ int main( void ) {
     int i;
 
     for ( i = 0; i < 25; i++ ) {
-        a = random_uniform( STDLIB_CONSTANT_FLOAT64_EPS, 10.0 );
-        b = random_uniform( STDLIB_CONSTANT_FLOAT64_EPS, 10.0 );
+        alpha = random_uniform( STDLIB_CONSTANT_FLOAT64_EPS, 10.0 );
+        beta = random_uniform( STDLIB_CONSTANT_FLOAT64_EPS, 10.0 );
         y = stdlib_base_dists_invgamma_mode( alpha, beta );
         printf( "α: %lf, β: %lf, mode(X;α,β): %lf\n", alpha, beta, y );
     }