devel/py-bullet3: fix build on powerpc64

In file included from examples/ThirdPartyLibs/Eigen/Core:211:
examples/ThirdPartyLibs/Eigen/src/Core/arch/AltiVec/PacketMath.h:1345:32: error: use of undeclared identifier 'vec_sqrt'; did you mean 'vec_rsqrte'?

BF16_TO_F32_UNARY_OP_WRAPPER(vec_sqrt, a);
                             ^~~~~~~~
                             vec_rsqrte