Update developer handbook to exclude C90

Author: lcartey

docs/development_handbook.md

@@ -82,7 +82,7 @@ For each supported coding standard we will provide:
 These packs will be organized by supported language.
 The current supported languages are:
 - C++14 standardized by [ISO/IEC 14882:2014](https://www.iso.org/standard/64029.html) located in the directory `cpp`.
-- C90 standardized by [ISO/IEC 9899:1990](https://www.iso.org/standard/17782.html), [C99] standardized by [ISO/IEC 9899:1999](https://www.iso.org/standard/29237.html), and C11 standardized by [ISO/IEC 9899:2011](https://www.iso.org/standard/57853.html). All are located in the directory `c`.
+- [C99] standardized by [ISO/IEC 9899:1999](https://www.iso.org/standard/29237.html) and C11 standardized by [ISO/IEC 9899:2011](https://www.iso.org/standard/57853.html). All are located in the directory `c`.
 
 For each language, we will also include:
  1. A CodeQL query pack containing "common" libraries, which provide support.