fix 07-find.cpp wrong output

[izikorgad]

The output for set was wrong.

The actual output is:

Before:
string: hello
vector: 1 9 7 3 
set: 3 4 6 8 
Found in string at position: 2
Found in vector: 7
Found in set: 6
After:
string: helo
vector: 1 9 3 
set: 3 4 8 

[izikorgad]

Fixing wrong output for 07-find.cpp

[cpp-tutor]

Thank you for this correction, I will also update the version on the blog.