Fix typos

[practicalswift]

Description

Fix typos.

Checklist:

• I understand README.md.
• If this is a feature addition, that feature has been voted into the C++
  Working Draft.
• Any code files edited have been processed by clang-format.
• Identifiers in any product code changes are properly _Ugly as per
  https://eel.is/c++draft/lex.name#3.1 .
• Identifiers in test code changes are not _Ugly.
• Test code includes the correct headers as per the Standard, not just
  what happens to compile.
• The STL builds and test harnesses have passed (must be manually verified
  by an STL maintainer before CI is online, leave this unchecked for initial
  submission).
• This change introduces no known ABI breaks (adding members, renaming
  members, adding virtual functions, changing whether a type is an aggregate or
  trivially copyable, etc.). If unsure, leave this box unchecked and ask a
  maintainer for help.

[msftclas]

All CLA requirements met.

[CaseyCarter]

There's some whitespace damage here - and in <memory> and <regex> - that suggests you're not using clang-format 8.0.1. I'll clean it up, but for future reference please use 8.0.1 so we don't have churn in the sources from competing versions of clang-format.

[CaseyCarter]

@practicalswift, it looks like you haven't yet signed our Contributor License Agreement (CLA). Unfortunately, we cannot accept contributions without the signed CLA.

[StephanTLavavej]

#103 updates the pull request template to provide proper guidance regarding clang-format version.

[StephanTLavavej]

Thank you! 😸