Normalize author links to use GitHub profile links.

These links are already in use for these authors in other proposals.

Author: dempseyatgithub

proposals/0199-bool-toggle.md

@@ -1,7 +1,7 @@
 # Adding `toggle` to `Bool`
 
 * Proposal: [SE-0199](0199-bool-toggle.md)
-* Author: [Chris Eidhof](http://chris.eidhof.nl)
+* Author: [Chris Eidhof](https://github.com/chriseidhof)
 * Review Manager: [Ben Cohen](https://github.com/airspeedswift/)
 * Status: **Implemented (Swift 4.2)**
 * Decision notes: [Rationale](https://forums.swift.org/t/accepted-se-199-add-toggle-to-bool/10681)

proposals/0266-synthesized-comparable-for-enumerations.md

@@ -1,7 +1,7 @@
 # Synthesized `Comparable` conformance for `enum` types
 
 * Proposal: [SE-0266](0266-synthesized-comparable-for-enumerations.md)
-* Author: [Dianna Ma (taylorswift)](https://forums.swift.org/u/taylorswift)
+* Author: [Dianna Ma (taylorswift)](https://github.com/tayloraswift)
 * Review Manager: [Ben Cohen](https://github.com/airspeedswift)
 * Status: **Implemented (Swift 5.3)**
 * Implementation: [apple/swift#25696](https://github.com/apple/swift/pull/25696)