osxaudio: misspelled dependency

When building osxaudio, the required 'AudioToolbox' dependency is
misspelled as 'AudioToolBox', which crashes the build with error:
ld: framework not found AudioToolBox
23 jobs for osx-misspell in 67 minutes and 57 seconds (queued for 8 minutes)
latest
Status Job ID Name Coverage
  Preparation
passed #514006
gst indent

00:00:57

passed #514005
manifest

00:01:17

 
  Build
passed #514015
build cerbero android universal

00:12:12

passed #514016
build cerbero cross win32

00:10:58

passed #514017
build cerbero cross win64

00:07:04

passed #514014
build cerbero fedora x86_64

00:11:54

manual #514019
gst-ios-12.2 allowed to fail manual
build cerbero ios universal
passed #514018
gst-macos-10.14
build cerbero macos x86_64

00:10:06

passed #514007
build fedora x86_64

00:07:36

passed #514013
docker windows 1607
build msys2

00:13:36

passed #514008
build nodebug fedora x86_64

00:05:20

passed #514009
build static fedora x86_64

00:15:13

passed #514187
build static nodebug fedora x86_64

00:12:59

passed #514011
docker windows 1607
build vs2017 amd64

00:11:55

passed #514012
docker windows 1607
build vs2017 x86

00:11:38

failed #514010
build static nodebug fedora x86_64

00:12:05

 
  Test
passed #514020
check fedora

00:04:38

passed #514021
integration testsuites fedora

00:15:47

passed #514023
valgrind bad

00:07:58

passed #514024
valgrind ges

00:07:24

passed #514022
valgrind good

00:16:56

 
  Integrate
passed #514025
android universal examples

00:07:46

passed #514026
documentation

00:06:09