Revert "sphinx: jit: port libgccjit to shared Sphinx"

gcc/jit/Make-lang.in

gcc/jit/doc/conf.py

gcc/jit/docs/Makefile

gcc/jit/docs/_build/texinfo/Makefile

gcc/jit/docs/_build/texinfo/libgccjit-figures/factorial.png

gcc/jit/docs/_build/texinfo/libgccjit-figures/factorial1.png

.../docs/_build/texinfo/libgccjit-figures/sum-of-squares.png

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gcc/jit/docs/_build/texinfo/libgccjit.texi

gcc/jit/docs/conf.py

gcc/jit/docs/cp/index.rst

gcc/jit/docs/cp/intro/index.rst

gcc/jit/docs/cp/intro/tutorial01.rst

gcc/jit/docs/cp/intro/tutorial02.rst

gcc/jit/docs/cp/intro/tutorial03.rst

gcc/jit/docs/cp/intro/tutorial04.rst

gcc/jit/docs/cp/topics/asm.rst

gcc/jit/docs/cp/topics/compilation.rst

gcc/jit/docs/cp/topics/contexts.rst

gcc/jit/docs/cp/topics/expressions.rst