User Guide Minor fix

Sphinx was complaining about the "title overline" for the contributing page entry "Tips for a good issue report". Fixed this.
Signed-off-by:James L Parry <jim_parry@bcit.ca>
diff --git a/user_guide_src/source/contributing/index.rst b/user_guide_src/source/contributing/index.rst
index c784a59..3548dbc 100644
--- a/user_guide_src/source/contributing/index.rst
+++ b/user_guide_src/source/contributing/index.rst
@@ -31,9 +31,9 @@
 If you are wondering if you are using 
 something correctly or if you have found a bug, ask on the forum first.
 
-***************************
+****************************
 Tips for a Good Issue Report
-***************************
+****************************
 
 Use a descriptive subject line (eg parser library chokes on commas) rather than a vague one (eg. your code broke).