[ruby/rubygems] update magnus version in rust extension gem template #712

Job	Run time
make (check, --enable-shared --enable-load-relative)	8m 27s
make (check, i686)	12m 12s
make (check, --disable-yjit)	7m 19s
make (test-bundler-parallel, 50)	29m 34s
make (check, cppflags=-DVM_CHECK_MODE)	8m 39s
make (check, ubuntu-24.04-arm, capi)	7m 26s
make (test-bundled-gems)	22m 28s
make (check, ubuntu-24.04, capi)	9m 20s
make-ibm	-1s
Ubuntu result	3s
	1h 45m 27s

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