test(io): drop Gmsh reader smoke tests

The in-tree `GmshReader` module is gone, so the dedicated IO test driver and
Tet4 fixture assertions are removed to keep the default suite aligned with
core dependencies.

- Delete `test/io/runtests.jl`, which only included `test_gmsh_reader.jl`
- Delete `test/io/test_gmsh_reader.jl`, which exercised `read_gmsh_mesh` and `get_surface_nodes` against bundled `.msh` data

test/io/runtests.jl

@@ -1,7 +0,0 @@
-# SPDX-FileCopyrightText: 2015-2026 Jukka Aho
-# SPDX-License-Identifier: MIT
-
-using Test
-using JuliaFEM
-
-include("test_gmsh_reader.jl")

test/io/test_gmsh_reader.jl

@@ -1,21 +0,0 @@
-# SPDX-FileCopyrightText: 2015-2026 Jukka Aho
-# SPDX-License-Identifier: MIT
-
-using Test
-using JuliaFEM.GmshReader: read_gmsh_mesh, get_surface_nodes
-
-@testset "GmshReader Tet4 (ASCII 4.1)" begin
-    path = joinpath(@__DIR__, "..", "testdata", "cantilever_beam.msh")
-    gm = read_gmsh_mesh(path)
-    @test size(gm.nodes, 1) == 3
-    @test size(gm.elements, 1) == 4
-    @test size(gm.nodes, 2) ≥ 1
-    @test size(gm.elements, 2) ≥ 1
-    @test haskey(gm.physical_groups, "Bulk")
-
-    fix = get_surface_nodes(gm, "FixedEnd")
-    top = get_surface_nodes(gm, "PressureSurface")
-    @test !isempty(fix)
-    @test !isempty(top)
-    @test isempty(get_surface_nodes(gm, "UnknownBoundary"))
-end