Fix minor typos

Signed-off-by: David A. Wheeler <[email protected]>

Author: david-a-wheeler

secure_software_development_fundamentals.md

@@ -28,13 +28,12 @@ The learning approach is designed to potentially support many users (with a pote
 This document is written to be easily understood by its audience (in this case, software developers). In general, in this document:
 
 * Use contractions (unless you want special emphasis on something).
-* Use logical quotation, not typographical quotation. Quotations only include what is quoted. For more, see the [Wikipedia: Logical quotation on Wikipedia](https://en.wikipedia.org/wiki/Wikipedia:Logical_quotation_on_Wikipedia).
+* Use logical quotation, not typographical quotation. Quotations only include what is quoted. For more, see [Wikipedia: Logical quotation on Wikipedia](https://en.wikipedia.org/wiki/Wikipedia:Logical_quotation_on_Wikipedia).
 * Use pronouns, especially *you*.
 * Cite sources.
 
 For more, see [5 Stupid Grammar Rules You Should Never Follow Because They Make Your Writing Worse](https://www.inc.com/minda-zetlin/5-stupid-grammar-rules-you-should-never-follow-because-they-make-your-writing-wo.html) and [6 Grammar Superstitions: The Never-Never Rules](https://wac.colostate.edu/docs/books/grammar/chapter6.pdf).
 
-
 Note that edX requires groupings at 3 levels: Sections, Subsections, and Units. Only Units (level 3) can have content.  We represent this in the material below as follows:  A “Heading 1” represents the beginning of a Section and contains ONLY sequences beginning with “Heading 2” (no text). A “Heading 2” represents the beginning of a Subsection and contains ONLY sequences beginning with “Heading 3”. A “Heading 3” represents the beginning of a Unit and contains all content. A Heading 3 cannot be directly contained within a Heading 1. Heading 4 (and below) are used freely within a Unit.
 
 **About this course (Part 1)**