EEschema: Fix visibility of sources on dialog "Spice Model Editor"

Description

On a dialog "Spice Model Editor", tab "Source" there are three tabs visible on Windows, but not on Linux. Following picture shows the expected behavior:

Steps to reproduce

1. Open Eeschema and add some component, passive or source.
2. Double click on a component to open dialog "Symbol Properties"
3. Click button "Spice Model..." on the bottom of window.
4. Go to the tab "Source"
5. Seven tabs should be visible in "Transient Analysis", including: FM, AM and Random, as shown above.

KiCad Version

Application: Eeschema

Version: (5.99.0-7220-g8633410bec-dirty), debug build

Libraries:
	wxWidgets 3.0.4
	libcurl/7.68.0 OpenSSL/1.1.1f zlib/1.2.11 brotli/1.0.7 libidn2/2.2.0 libpsl/0.21.0 (+libidn2/2.2.0) libssh/0.9.3/openssl/zlib nghttp2/1.40.0 librtmp/2.3

Platform: Linux 5.4.0-53-generic x86_64, 64 bit, Little endian, wxGTK, KDE, x11

Build Info:
	Date: Nov 28 2020 17:17:01
	wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.71.0
	Curl: 7.68.0
	ngspice: 31
	Compiler: GCC 9.3.0 with C++ ABI 1013

Build settings:
	KICAD_SCRIPTING=OFF
	KICAD_SCRIPTING_MODULES=OFF
	KICAD_SCRIPTING_PYTHON3=OFF
	KICAD_SCRIPTING_WXPYTHON=OFF
	KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
	KICAD_SCRIPTING_ACTION_MENU=OFF
	KICAD_SPICE=ON
	KICAD_STDLIB_DEBUG=OFF
	KICAD_STDLIB_LIGHT_DEBUG=OFF
	KICAD_SANITIZE=OFF