integrations: Change integrations content.

We remove the title from `errbot` integration documentation so that
all documentations have the same style.  See
https://github.com/zulip/python-zulip-api/pull/515 for a similar
change to integrations where the docs live elsewhere in version control.

We also remove the `margin: 0` from the instruction tip because where
the tip is followed by a list, there is no space between the two; this
change doesn't mess up the other places where the tip is used.

static/styles/portico/portico.scss

@@ -1721,7 +1721,6 @@ input.new-organization-button {
     border: 1px solid hsl(46, 63%, 84%);
 }
 
-.integration-instructions .tip,
 .markdown .warn p,
 .markdown .tip p,
 .markdown .keyboard_tip p {

templates/zerver/integrations/errbot.md

@@ -1,4 +1,4 @@
-# Run your favorite chatbot in Zulip!
+Run your favorite chatbot in Zulip!
 
 0. [Install errbot](http://errbot.io/en/latest/user_guide/setup.html)
    and follow to instructions to setup a `config.py`.
@@ -43,7 +43,6 @@
 
 ![](/static/images/integrations/errbot/000.png)
 
-Tips
-----
+### Tips
 
 * Rooms in ErrBot are streams in Zulip.