Bump upper bound on primitive.

[philderbeast]

I tried #307 (just merged) in a project that references stackage (nightly-2023-05-03 for ghc-9.4.5):

$ cabal build all --enable-tests --enable-benchmarks
HEAD is now at 7b94c5a Fix for machines with 64bit word and base >= 4.17
Resolving dependencies...
Error: cabal: Could not resolve dependencies:
[__0] trying: cborg-0.2.8.0 (user goal)
[__1] next goal: primitive (dependency of cborg)
[__1] rejecting: primitive-0.8.0.0 (conflict: cborg => primitive>=0.5 && <0.8)
[__1] rejecting: primitive-0.7.4.0, primitive-0.7.3.0, primitive-0.7.2.0,
primitive-0.7.1.0, primitive-0.7.0.1, primitive-0.7.0.0, primitive-0.6.4.0,
primitive-0.6.1.1, primitive-0.6.1.0, primitive-0.5.4.0, primitive-0.5.3.0,
primitive-0.5.2.1, primitive-0.5.1.0, primitive-0.5.0.1, primitive-0.5,
primitive-0.4.1, primitive-0.4.0.1, primitive-0.4, primitive-0.3.1,
primitive-0.3, primitive-0.2.1, primitive-0.2, primitive-0.1,
primitive-0.6.3.0, primitive-0.6.2.0, primitive-0.6.1.2, primitive-0.6
(constraint from project config ./.../nightly-2023-05-03.config
requires ==0.8.0.0)
[__1] fail (backjumping, conflict set: cborg, primitive)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: primitive, cborg

To fix that, I bumped the upper bound on primitive.