[Changelog] Add SE-0253: `func callAsFunction`. (#26866)
[Changelog] Add SE-0253: `func callAsFunction`. (#26866)

Changelog entry for SE-0253.
Follow-up to implementation: https://github.com/apple/swift/pull/24299.
gregomni/swift,CodaFi/swift,jckarter/swift,ahoppen/swift,devincoughlin/swift,tkremenek/swift,hooman/swift,stephentyrone/swift,jckarter/swift,atrick/swift,CodaFi/swift,nathawes/swift,parkera/swift,lorentey/swift,parkera/swift,harlanhaskins/swift,parkera/swift,rudkx/swift,lorentey/swift,sschiau/swift,xwu/swift,devincoughlin/swift,jmgc/swift,sschiau/swift,airspeedswift/swift,karwa/swift,roambotics/swift,karwa/swift,parkera/swift,stephentyrone/swift,nathawes/swift,jmgc/swift,CodaFi/swift,CodaFi/swift,rudkx/swift,apple/swift,glessard/swift,gregomni/swift,jckarter/swift,ahoppen/swift,stephentyrone/swift,lorentey/swift,glessard/swift,JGiola/swift,harlanhaskins/swift,jmgc/swift,glessard/swift,roambotics/swift,jmgc/swift,rudkx/swift,JGiola/swift,atrick/swift,JGiola/swift,aschwaighofer/swift,xwu/swift,tkremenek/swift,gregomni/swift,allevato/swift,sschiau/swift,benlangmuir/swift,hooman/swift,gribozavr/swift,nathawes/swift,tkremenek/swift,apple/swift,gribozavr/swift,roambotics/swift,ahoppen/swift,atrick/swift,devincoughlin/swift,devincoughlin/swift,jckarter/swift,gribozavr/swift,airspeedswift/swift,gribozavr/swift,hooman/swift,lorentey/swift,karwa/swift,jmgc/swift,aschwaighofer/swift,tkremenek/swift,allevato/swift,devincoughlin/swift,jmgc/swift,ahoppen/swift,gregomni/swift,sschiau/swift,parkera/swift,lorentey/swift,benlangmuir/swift,jckarter/swift,gribozavr/swift,airspeedswift/swift,jckarter/swift,harlanhaskins/swift,gregomni/swift,harlanhaskins/swift,karwa/swift,xwu/swift,apple/swift,allevato/swift,aschwaighofer/swift,airspeedswift/swift,stephentyrone/swift,harlanhaskins/swift,karwa/swift,rudkx/swift,glessard/swift,hooman/swift,ahoppen/swift,allevato/swift,lorentey/swift,aschwaighofer/swift,apple/swift,roambotics/swift,parkera/swift,apple/swift,benlangmuir/swift,harlanhaskins/swift,allevato/swift,glessard/swift,tkremenek/swift,roambotics/swift,karwa/swift,CodaFi/swift,allevato/swift,airspeedswift/swift,hooman/swift,atrick/swift,devincoughlin/swift,atrick/swift,aschwaighofer/swift,sschiau/swift,gregomni/swift,hooman/swift,benlangmuir/swift,stephentyrone/swift,glessard/swift,roambotics/swift,sschiau/swift,devincoughlin/swift,stephentyrone/swift,hooman/swift,JGiola/swift,aschwaighofer/swift,jckarter/swift,aschwaighofer/swift,JGiola/swift,apple/swift,rudkx/swift,xwu/swift,devincoughlin/swift,gribozavr/swift,jmgc/swift,tkremenek/swift,harlanhaskins/swift,sschiau/swift,nathawes/swift,ahoppen/swift,nathawes/swift,nathawes/swift,karwa/swift,gribozavr/swift,airspeedswift/swift,CodaFi/swift,allevato/swift,lorentey/swift,parkera/swift,xwu/swift,atrick/swift,JGiola/swift,nathawes/swift,sschiau/swift,stephentyrone/swift,karwa/swift,benlangmuir/swift,lorentey/swift,rudkx/swift,tkremenek/swift,benlangmuir/swift,gribozavr/swift,xwu/swift,CodaFi/swift,xwu/swift,airspeedswift/swift,parkera/swift