Fix dialyzer_opts documentation

rebar.config.sample

@@ -85,7 +85,7 @@
 %% {plt, PltFile}
 %% 'src': run Dialyzer on the source files as in 'dialyzer --src'
 %% {warnings, [WarnOpts]}: turn on/off Dialyzer warnings
-{warnings_opts, [{plt, PltFile}, {warnings, [WarnOpts]}, src]}.
+{dialyzer_opts, [{plt, PltFile}, {warnings, [WarnOpts]}, src]}.
 
 %% == Cleanup ==