remove const for copy_source_bucket #3803

Job	Run time
byo-crypto	3m 1s
clang-sanitizers (,thread)	18m 27s
downstream	17m 7s
linux-compat (manylinux1-x64)	16m 57s
clang-sanitizers (,address,undefined)	18m 1s
linux-compat (manylinux1-x86)	17m 47s
linux-compat (manylinux2014-x64)	17m 4s
linux-debug	16m 41s
linux-compiler-compat (clang-3)	17m 11s
linux-shared-libs	16m 53s
linux-compiler-compat (clang-6)	17m 41s
linux-compiler-compat (clang-8)	17m 58s
macos	13m 54s
linux-compat (manylinux2014-x86)	16m 18s
linux-compiler-compat (clang-9)	18m 19s
macos-x64	15m 30s
linux-compat (al2-x64)	16m 11s
linux-compiler-compat (clang-10)	16m 53s
linux-compiler-compat (clang-11)	17m 3s
windows	18m 45s
windows-app-verifier	34m 0s
linux-compiler-compat (clang-15)	18m 20s
windows-shared-libs	17m 8s
linux-compiler-compat (clang-17)	18m 55s
windows-vc14 (x86)	15m 34s
linux-compiler-compat (gcc-4.8)	16m 3s
windows-vc14 (x64)	15m 52s
linux-compiler-compat (gcc-5)	17m 3s
linux-compiler-compat (gcc-6)	15m 59s
linux-compiler-compat (gcc-7)	17m 10s
linux-compiler-compat (gcc-8)	17m 59s
linux-compiler-compat (gcc-11)	18m 34s
linux-compiler-compat (gcc-13, --cmake-extra=-DCMAKE_EXE_LINKER_FLAGS="-lresolv")	20m 15s
	9h 30m 33s

Provide feedback