Correct syntax error in docs.

docs/developer-guide.txt

@@ -45,7 +45,7 @@ ticket already exists for your issue. If not, create one. Try to think from
 the perspective of the reader. Explain what behavior you expected, what you
 got instead, and what factors might have contributed to the unexpected
 behavior. In Bitbucket, surround a block of code or traceback with the triple
-backtick "```" so that it is formatted nicely.
+backtick "\`\`\`" so that it is formatted nicely.
 
 Filing a ticket provides a forum for justification, discussion, and
 clarification. The ticket provides a record of the purpose for the change and