docs: fix incorrect return value in stats/base/dists/exponenetial/logpdf/README.md

PR-URL: #10963

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

Author: Om-A-osc

lib/node_modules/@stdlib/stats/base/dists/exponential/logpdf/README.md

@@ -166,7 +166,7 @@ Evaluates the natural logarithm of the [probability density function][pdf] (PDF)
 
 ```c
 double out = stdlib_base_dists_exponential_logpdf( 2.0, 0.7 );
-// returns ~0.173
+// returns ~-1.757
 ```
 
 The function accepts the following arguments: