docs: update stats/base/dists/truncated-normal to use Greek symbols

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---

Author: Planeshifter

lib/node_modules/@stdlib/stats/base/dists/truncated-normal/pdf/README.md

@@ -137,7 +137,7 @@ for ( i = 0; i < 25; i++ ) {
     mu = ( randu() * 20.0 ) - 10.0;
     sigma = ( randu() * 10.0 ) + 2.0;
     y = pdf( x, a, b, mu, sigma );
-    console.log( 'x: %d, a: %d, b: %d, mu: %d, sigma: %d, f(x;a,b,mu,sigma): %d', x.toFixed( 4 ), a.toFixed( 4 ), b.toFixed( 4 ), mu.toFixed( 4 ), sigma.toFixed( 4 ), y.toFixed( 4 ) );
+    console.log( 'x: %d, a: %d, b: %d, µ: %d, σ: %d, f(x;a,b,µ,σ): %d', x.toFixed( 4 ), a.toFixed( 4 ), b.toFixed( 4 ), mu.toFixed( 4 ), sigma.toFixed( 4 ), y.toFixed( 4 ) );
 }
 ```
 

lib/node_modules/@stdlib/stats/base/dists/truncated-normal/pdf/examples/index.js

@@ -36,5 +36,5 @@ for ( i = 0; i < 25; i++ ) {
 	mu = ( randu() * 20.0 ) - 10.0;
 	sigma = ( randu() * 10.0 ) + 2.0;
 	y = pdf( x, a, b, mu, sigma );
-	console.log( 'x: %d, a: %d, b: %d, mu: %d, sigma: %d, f(x;a,b,mu,sigma): %d', x.toFixed( 4 ), a.toFixed( 4 ), b.toFixed( 4 ), mu.toFixed( 4 ), sigma.toFixed( 4 ), y.toFixed( 4 ) );
+	console.log( 'x: %d, a: %d, b: %d, µ: %d, σ: %d, f(x;a,b,µ,σ): %d', x.toFixed( 4 ), a.toFixed( 4 ), b.toFixed( 4 ), mu.toFixed( 4 ), sigma.toFixed( 4 ), y.toFixed( 4 ) );
 }