Remove discontinued channel apps from customApps.js

The source files for several channel apps were removed in 40b02b3, but
these were still referenced in customApps.js.

Custom thumbnails and icons for these channels are still in the
repository, so they are not changed here.

https://phabricator.endlessm.com/T35147

kolibri_explore_plugin/assets/src/customApps.js

@@ -39,7 +39,6 @@ export const CustomChannelApps = {
   '2f95235c3709511fa12d007f31ed6a7b': 'steam',
   '1520f018610256549c98ca0140cceebe': 'virtual-field-trips',
   eb4373b5da054c07879d0c969dc1976a: 'virtual-science-teachers',
-  '59b8deeb90f544da923187e77c8d3820': 'wikihow',
   '1b1fc9bd453a4c52bb5628d9ae804ede': 'scigirls', // scigirls english
   ee52db4a62a94e9683599af8782f2d03: 'scigirls', // scigirls spanish
   f1ada7abc4194ff48a958337a31972c7: 'eie-families', // eie english
@@ -103,7 +102,6 @@ export const EkIguanaSections = [
     name: 'Games & Gaming',
     channels: [
       '3160899a73564d8a8467284d9219b91c', // terminal-two
-      '38eaaf9ec82a44f9ab6e7a44cb730f07', // pbs-kids
       '57e23812e0dc562581958e39acedd717', // gaming
       'ed519e3b798147569b46cb550dbfc373', // blockly-games
     ],
@@ -115,7 +113,6 @@ export const EkIguanaSections = [
       'f5f6729f95b55753badeaa066fa6e986', // healthy-body
       '4e413158eac55422a5343af9fcfa8d59', // healthy-mind
       '3fcffebc58d15175b948b140434ef6e6', // sports
-      'c8540424d77f44f8ae306e22d3b14eaf', // coronavirus
     ],
     contentPicks: [],
   },
@@ -124,7 +121,6 @@ export const EkIguanaSections = [
     channels: [
       '97111903de564de49483a9705d41a8ac', // career-girls
       '2b43973f53f1538bad5ece63ad847606', // financial-literacy
-      '9eeebbc5140d5b98ac4a4d2ce9432135', // lgbtq
       '79a50be66bad5eb686c42617c914fd45', // careers
     ],
     contentPicks: [],
@@ -141,7 +137,6 @@ export const EkIguanaSections = [
   {
     name: 'Literature and Language Arts',
     channels: [
-      '59bb2e5a3d2e5e3b85b87d9ab4daa2f3', // reading
       '914fee213ee146de869016c287116b23', // novels
       '0418cc231e9c5513af0fff9f227f7172', // hello-channel
       '74f36493bb475b62935fa8705ed59fed', // thoughtful-learning