Minor changes to sample letter of submittal.

- Capitalized "St." in the address.
- Made "work report" lowercase.
- Added "the" in "…that the Co-operative Education Program requires that I…"
- Switched order of BMath and Co-op to match faculty sample [1]. 
- Fixed typo "requiremends" => "requirements".
- Added note about having to sign the letter of submittal [1].

[1] - see section 3.3 of https://math.uwaterloo.ca/math/current-undergraduates/co-op-information/work-report-guidelines/30-work-report-structure.