docs: add missing period

Signed-off-by: Philipp Burckhardt <[email protected]>

Author: Planeshifter

lib/node_modules/@stdlib/stats/base/dists/chi/variance/README.md

@@ -153,7 +153,7 @@ double out = stdlib_base_dists_chi_variance( 9.0 );
 
 The function accepts the following arguments:
 
--   **k**: `[in] double` degrees of freedom
+-   **k**: `[in] double` degrees of freedom.
 
 ```c
 double stdlib_base_dists_chi_variance( const double k );