Raise LinearSolve compat floor to 4.3.0 in the two touched sublibraries

The old 3.75.0 floor was inconsistent with the NonlinearSolveBase 2.34.1 floor,
which itself requires LinearSolve >= 4.3.0, so the declared minimum versions
were mutually unsatisfiable (this is what the Downgrade Sublibraries CI hits).
Raising the LinearSolve floor to 4.3.0 makes the metadata consistent for these
two libraries without dropping any actually-installable configuration. The
warm-start resolver remains guarded on isdefined(LinearSolve, :WarmStart), so it
still no-ops on LinearSolve 4.x and activates on 5.1+.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: ChrisRackauckas

lib/OrdinaryDiffEqDifferentiation/Project.toml

@@ -21,7 +21,7 @@ DiffEqDevTools = "3"
 Test = "<0.0.1, 1"
 FiniteDiff = "2.27"
 DifferentiationInterface = "0.7.18"
-LinearSolve = "3.75.0, 4, 5"
+LinearSolve = "4.3.0, 5"
 ConstructionBase = "1.5.8"
 LinearAlgebra = "1.10"
 SciMLBase = "3.35.1"

lib/OrdinaryDiffEqNonlinearSolve/Project.toml

@@ -58,7 +58,7 @@ FastBroadcast = "1.3"
 Random = "<0.0.1, 1"
 DiffEqDevTools = "3"
 MuladdMacro = "0.2.4"
-LinearSolve = "3.75.0, 4, 5"
+LinearSolve = "4.3.0, 5"
 LineSearches = "7.5.1"
 LinearAlgebra = "1.10"
 OrdinaryDiffEqDifferentiation = "3"