main: Fix memleaks in mesa_use_program

Add freeing of SubroutineIndexes to the _mesa_free_shader_state.

Fixes: 4566aaaa ("mesa/subroutines: start adding per-context
subroutine index support (v1.1)")
Signed-off-by: Yevhenii Kolesnikov <yevhenii.kolesnikov@globallogic.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
13 jobs for !1326 with fix/memleak_SubroutineIndex in 17 minutes and 1 second (queued for 10 seconds)
latest detached
Status Job ID Name Coverage
  Containers Build
passed #444475
debian

00:00:43

 
  Build+Test
passed #444484
meson-arm64

00:02:07

passed #444483
meson-armhf

00:02:31

passed #444477
meson-clang

00:04:08

passed #444481
meson-clover

00:09:11

passed #444485
meson-i386

00:01:43

passed #444480
meson-main

00:06:11

passed #444476
meson-swr-glvnd

00:06:46

passed #444482
meson-vulkan

00:01:44

passed #444487
scons-llvm

00:06:12

passed #444486
scons-nollvm

00:03:25

passed #444478
scons-swr

00:06:02

passed #444479
scons-win64

00:06:32