[llvm-readobj][test] - Remove --symbols --dyn-syms part from Object/readobj-shared-object.test.

The intention of Object/readobj-shared-object.test was to check the
general output for shared object.

I've added a case for testing dynamic objects to ELF/symbols.test.
Also we already test dynamic symbols printing in ELF/dyn-symbols.test +
I've added a case for `--dyn-syms` alias in D73164.

Hence we can remove this piece from Object/readobj-shared-object.test.

Differential revision: https://reviews.llvm.org/D73175