fix: use Greek symbols in C printf format strings

---
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---

Author: Planeshifter

lib/node_modules/@stdlib/stats/base/dists/lognormal/pdf/README.md

@@ -229,7 +229,7 @@ int main( void ) {
         mu = random_uniform( -5.0, 5.0 );
         sigma = random_uniform( STDLIB_CONSTANT_FLOAT64_EPS, 5.0 );
         y = stdlib_base_dists_lognormal_pdf( x, mu, sigma );
-        printf( "x: %lf, mu: %lf, sigma: %lf, f(x;mu,sigma): %lf\n", x, mu, sigma, y );
+        printf( "x: %lf, μ: %lf, σ: %lf, f(x;μ,σ): %lf\n", x, mu, sigma, y );
     }
 }
 ```

lib/node_modules/@stdlib/stats/base/dists/lognormal/pdf/examples/c/example.c

@@ -38,6 +38,6 @@ int main( void ) {
 		mu = random_uniform( -5.0, 5.0 );
 		sigma = random_uniform( STDLIB_CONSTANT_FLOAT64_EPS, 5.0 );
 		y = stdlib_base_dists_lognormal_pdf( x, mu, sigma );
-		printf( "x: %lf, mu: %lf, sigma: %lf, f(x;mu,sigma): %lf\n", x, mu, sigma, y );
+		printf( "x: %lf, μ: %lf, σ: %lf, f(x;μ,σ): %lf\n", x, mu, sigma, y );
 	}
 }