common/logging: Amend documentation comments

Multi-line doc comments still need the '<' after the ///, otherwise it's
treated as a regular comment and makes the original doc comment broken
in viewers, IDEs, etc. While we're at it, also fix some typos in the
comments.

src/common/logging/text_formatter.h

@@ -15,6 +15,6 @@ struct Entry;
 std::string FormatLogMessage(const Entry& entry);
 /// Formats and prints a log entry to stderr.
 void PrintMessage(const Entry& entry);
-/// Prints the same message as `PrintMessage`, but colored acoording to the severity level.
+/// Prints the same message as `PrintMessage`, but colored according to the severity level.
 void PrintColoredMessage(const Entry& entry);
 } // namespace Log