docs: Stop building the doc cache by default

Fixes gstreamer/gst-docs#36
16 jobs for doc_fixes in 87 minutes and 18 seconds (queued for 4 minutes and 45 seconds)
Status Job ID Name Coverage
  Preparation
passed #303157
gst indent

00:00:57

passed #303156
manifest

00:00:39

 
  Build
passed #303158
build fedora x86_64

00:06:10

passed #303159
build nodebug fedora x86_64

00:06:10

 
  Test
passed #303160
check fedora

00:04:57

passed #303161
integration testsuites fedora

00:09:49

 
  Full Builds
passed #303163
build cerbero android universal

00:18:24

passed #303164
build cerbero cross win32

00:07:17

passed #303165
build cerbero cross win64

00:05:31

passed #303162
build cerbero fedora x86_64

00:08:55

 
  Full Tests
passed #303167
valgrind bad

00:07:31

passed #303168
valgrind ges

00:11:09

passed #303495
valgrind good

00:10:45

failed #303166
valgrind good

00:10:22

 
  Apps
passed #303169
android universal examples

00:08:51

 
  Deploy
passed #303170
documentation

00:03:18