Fix G23H dist_dr3 jitter using DR2 proper motion mean instead of DR3

When user-supplied jitter terms (σ_dr3_pmra/σ_dr3_pmdec) were being fit,
the rebuilt dist_dr3 MvNormal was incorrectly centered on DR2 proper
motion values (pmra_dr2, pmdec_dr2) instead of DR3 values. This was a
copy-paste error from the DR2 block above.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sefffal

src/likelihoods/g23h.jl

@@ -738,7 +738,7 @@ function ln_like(like::G23HObs, ctx::SystemObservationContext)
                 pmra_var = like.catalog.pmra_dr3_error[1]^2 + (hasproperty(θ_obs, :σ_dr3_pmra) ? θ_obs.σ_dr3_pmra : zero(T))^2
                 pmdec_var = like.catalog.pmdec_dr3_error[1]^2 + (hasproperty(θ_obs, :σ_dr3_pmdec) ? θ_obs.σ_dr3_pmdec : zero(T))^2
                 dist_dr3 = MvNormal(
-                    @SVector([like.catalog.pmra_dr2, like.catalog.pmdec_dr2]),
+                    @SVector([like.catalog.pmra_dr3, like.catalog.pmdec_dr3]),
                     @SArray[
                         pmra_var c
                         c pmdec_var