Remove duplicate build configuration for ARM64/AAPCS/ELF

[SvenWehner]

Remove duplicate entry from Jamfile.v2 that prevented the selection of fcontext implementation with the following configuration:

<abi>aapcs <address-model>64 <architecture>arm <binary-format>mach-o <threading>multi <toolset>gcc

The error was as follows:

error: No best alternative for …/libs/context/build/asm_sources with <abi>aapcs <address-model>64 <architecture>arm <asynch-exceptions>off <binary-format>mach-o <boost.beast.allow-deprecated>on <boost.beast.separate-compilation>on <boost.cobalt.executor>any_io_executor <boost.cobalt.pmr>std <boost.process.fs>boost <context-impl>fcontext <coverage>off <debug-symbols>off <exception-handling>on <extern-c-nothrow>off <inlining>full <known-warnings>hide <link>shared <optimization>speed <os>MACOSX <pch>on <preserve-test-targets>on <profiling>off <python-debugging>off <python>3.14 <relevant>abi <relevant>address-model <relevant>architecture <relevant>binary-format <relevant>toolset <rtti>on <runtime-debugging>off <runtime-link>shared <stdlib>native <strip>off <target-os>darwin <testing.execute>on <threadapi>pthread <threading>multi <toolset-gcc:version>15 <toolset>gcc <variant>release <vectorize>off <visibility>hidden <warnings-as-errors>off <warnings>on <x-deduced-platform>arm_64
    no match: <abi>aapcs <address-model>32 <architecture>arm <binary-format>elf <threading>multi <toolset>clang
    no match: <abi>aapcs <address-model>32 <architecture>arm <binary-format>elf <threading>multi <toolset>gcc
    no match: <abi>aapcs <address-model>32 <architecture>arm <binary-format>elf <threading>multi <toolset>qcc
    no match: <abi>aapcs <address-model>32 <architecture>arm <binary-format>mach-o <threading>multi <toolset>clang
    matched: <abi>aapcs <address-model>64 <architecture>arm <binary-format>mach-o <threading>multi <toolset>gcc
    no match: <abi>aapcs <address-model>32 <architecture>arm <binary-format>mach-o <threading>multi <toolset>darwin
    no match: <abi>aapcs <address-model>32 <architecture>arm <binary-format>pe <threading>multi <toolset>msvc
    no match: <abi>aapcs <address-model>64 <architecture>arm <binary-format>elf <threading>multi <toolset>clang
    no match: <abi>aapcs <address-model>64 <architecture>arm <binary-format>elf <threading>multi <toolset>gcc
    no match: <abi>aapcs <address-model>64 <architecture>arm <binary-format>mach-o <threading>multi <toolset>clang
    no match: <abi>aapcs <address-model>64 <architecture>arm <binary-format>mach-o <threading>multi <toolset>darwin
    matched: <abi>aapcs <address-model>64 <architecture>arm <binary-format>mach-o <threading>multi <toolset>gcc

The duplicate code was introduced in d81d611 and 35ddf21.