Mentoring-Guide: replace 'student' with 'contributor'

Related to #555

The GSoC has been open to people who are not student for some time now,
so it's better if we standardize on using "applicant" for people not
yet accepted in the GSoC or Outreachy, and on using "contributor" as
Google does for people accepted in the GSoC.

Mentoring-Program-Guide.md

@@ -35,7 +35,7 @@ actually starts, (GSoC calls this the "Community Bonding" period,) is a
 blog.
 
 You might want to check which blogging tools previous Outreachy
-interns and GSoC students used. Using a Git related tools is of course
+interns and GSoC contributors used. Using a Git related tools is of course
 a good idea.
 
 - [Miriam Rubio's Outreachy intership experiences](https://mirucam.gitlab.io/outreachy_blog/)
@@ -110,15 +110,15 @@ mailing list, it is important that you cover all the following topics:
 4. what things you think should be easier
 5. what you are planning to work on and how
 
-The reason we ask for 2), 3) and 4) is that often interns or students
-don't know about things, like existing documentation, historical
-discussions, debugging scripts, features, tools or techniques, that
-could help them understand what's going on, or work in a more
-efficient way. If a mentor doesn't know that the intern or student is
-blocked or slowed by something or has a hard time moving forward, it's
-difficult for the mentor to help. So it's important for interns or
-students to reflect on the issues, blocks, inefficiencies, complex
-things that they are facing.
+The reason we ask for 2), 3) and 4) is that often interns or
+contributors don't know about things, like existing documentation,
+historical discussions, debugging scripts, features, tools or
+techniques, that could help them understand what's going on, or work
+in a more efficient way. If a mentor doesn't know that the intern or
+contributor is blocked or slowed by something or has a hard time
+moving forward, it's difficult for the mentor to help. So it's
+important for interns or contributors to reflect on the issues,
+blocks, inefficiencies, complex things that they are facing.
 
 Notifying the mailing list or your mentors about a blog post, should
 not prevent you from emailing or contacting the mailing list or your
@@ -178,9 +178,9 @@ list that people debug together or discuss together
 something over email in a very real-time way (at least similar as
 instant messaging chat).
 
-Such chats can sometimes help a student or intern (or even long timers
-on the project) move very fast in a short amount of time. So consider
-taking advantage of that.
+Such chats can sometimes help a contributor or intern (or even long
+timers on the project) move very fast in a short amount of time. So
+consider taking advantage of that.
 
 It's also easier for mentors to help (or understand how they could
 help) when discussing informally using a real time or near real time