pgsql: Fix allocation formula in llvmjit_expr.c

Fix allocation formula in llvmjit_expr.c

An array of LLVMBasicBlockRef is allocated with the size used for an
element being "LLVMBasicBlockRef *" rather than "LLVMBasicBlockRef".
LLVMBasicBlockRef is a type that refers to a pointer, so this did not
directly cause a problem because both should have the same size, still
it is incorrect.

This issue has been spotted while reviewing a different patch, and
exists since 2a0faed9d702, so backpatch all the way down.

Discussion: https://postgr.es/m/CA+hUKGLngd9cKHtTUuUdEo2eWEgUcZ_EQRbP55MigV2t_zTReg@mail.gmail.com
Backpatch-through: 14

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/5a4dc4aabd0345a194d27219f2424eb3dd3bf8fb

Modified Files
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src/backend/jit/llvm/llvmjit_expr.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)