RISC-V: testsuite: Remove deprecated compatibility headers

RISC-V: testsuite: Remove deprecated compatibility headers

Since r15-4981-g5c34f02ba7e these tests have been failing on vector
targets with excess errors due to the new deprecation warning message.
Remove the <cstdalign> header.

gcc/testsuite/ChangeLog:

	* g++.target/riscv/rvv/base/bug-10.C: Remove cstdalign header.
	* g++.target/riscv/rvv/base/bug-11.C: Ditto.
	* g++.target/riscv/rvv/base/bug-12.C: Ditto.
	* g++.target/riscv/rvv/base/bug-13.C: Ditto.
	* g++.target/riscv/rvv/base/bug-14.C: Ditto.
	* g++.target/riscv/rvv/base/bug-15.C: Ditto.
	* g++.target/riscv/rvv/base/bug-16.C: Ditto.
	* g++.target/riscv/rvv/base/bug-17.C: Ditto.
	* g++.target/riscv/rvv/base/bug-2.C: Ditto.
	* g++.target/riscv/rvv/base/bug-23.C: Ditto.
	* g++.target/riscv/rvv/base/bug-3.C: Ditto.
	* g++.target/riscv/rvv/base/bug-4.C: Ditto.
	* g++.target/riscv/rvv/base/bug-5.C: Ditto.
	* g++.target/riscv/rvv/base/bug-6.C: Ditto.
	* g++.target/riscv/rvv/base/bug-7.C: Ditto.
	* g++.target/riscv/rvv/base/bug-8.C: Ditto.
	* g++.target/riscv/rvv/base/bug-9.C: Ditto.

Signed-off-by: Edwin Lu <ewlu@rivosinc.com>