DOC: unwanted line of text
#### Location of the documentation
[./doc/source/development/contributing.rst](https://github.com/pandas-dev/pandas/blob/master/doc/source/development/contributing.rst#bug-reports-and-enhancement-requests)

#### Documentation problem
There seems to be an [unwanted line of text](https://github.com/pandas-dev/pandas/blob/master/doc/source/development/contributing.rst) at the top of the document: "{{ header }}"

#### Suggested fix for documentation
[I fixed it in my fork](https://github.com/benji1123/pandas/blob/master/doc/source/development/contributing.rst) and can make a PR (into master?).