Remove section 3 slide: 'Merging the Feature In'

The first task in section 4 is a code review exercise, which instructs
the students to open a pull request on GitHub. However, this slide
at the end of section 3 instructs the students to merge their changes
into develop locally.

This caused some confusion last time I ran this, as the students had no
existing changes to make a pull request from!

Author: hsaunders1904

slides/section_3_software_dev_process.md

@@ -855,20 +855,6 @@ Time: 10min
 
 <!-- #endregion -->
 
-<!-- #region slideshow={"slide_type": "subslide"} editable=true -->
-### Merge the Feature In
-
-Hopefully you have now refactored the feature to conform to our MVC structure, and ran our regression tests to check that the outputs rermain the same.
-
-We can commit this to our branch, and then switch to the `develop` branch and merge it in.
-
-```bash
-$ git switch develop
-$ git merge full-data-analysis
-```
-
-<!-- #endregion -->
-
 <!-- #region slideshow={"slide_type": "subslide"} editable=true -->
 ### Controller Structure