python3-matplotlib: add missing dependency

In order to fix the dependency issue on PIL module, python3-pillow is required.

Signed-off-by: Adrian Fiergolski <adrian.fiergolski@fastree3d.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-python/recipes-devtools/python/python3-matplotlib_3.5.1.bb

@@ -50,6 +50,7 @@ RDEPENDS:${PN} = "\
     ${PYTHON_PN}-dateutil \
     ${PYTHON_PN}-kiwisolver \
     ${PYTHON_PN}-pytz \
+    ${PYTHON_PN}-pillow \
 "
 
 ENABLELTO:toolchain-clang:riscv64 = "echo enable_lto = False >> ${S}/mplsetup.cfg"