fix(curriculum): add isHidden: false to challenges

This includes certificates (where it does nothing), but does not
include any translations.

curriculum/challenges/english/08-coding-interview-prep/algorithms/find-the-symmetric-difference.english.md

@@ -2,6 +2,7 @@
 id: a3f503de51cf954ede28891d
 title: Find the Symmetric Difference
 challengeType: 5
+isHidden: false
 forumTopicId: 301611
 ---
 

curriculum/challenges/english/08-coding-interview-prep/algorithms/implement-bubble-sort.english.md

@@ -2,6 +2,7 @@
 id: 8d5123c8c441eddfaeb5bdef
 title: Implement Bubble Sort
 challengeType: 1
+isHidden: false
 forumTopicId: 301612
 ---
 

curriculum/challenges/english/08-coding-interview-prep/algorithms/implement-insertion-sort.english.md

@@ -2,6 +2,7 @@
 id: 587d8259367417b2b2512c86
 title: Implement Insertion Sort
 challengeType: 1
+isHidden: false
 forumTopicId: 301613
 ---
 

curriculum/challenges/english/08-coding-interview-prep/algorithms/implement-merge-sort.english.md

@@ -2,6 +2,7 @@
 id: 587d825c367417b2b2512c8f
 title: Implement Merge Sort
 challengeType: 1
+isHidden: false
 forumTopicId: 301614
 ---
 

curriculum/challenges/english/08-coding-interview-prep/algorithms/implement-quick-sort.english.md

@@ -2,6 +2,7 @@
 id: 587d825a367417b2b2512c89
 title: Implement Quick Sort
 challengeType: 1
+isHidden: false
 forumTopicId: 301615
 ---
 

curriculum/challenges/english/08-coding-interview-prep/algorithms/implement-selection-sort.english.md

@@ -2,6 +2,7 @@
 id: 587d8259367417b2b2512c85
 title: Implement Selection Sort
 challengeType: 1
+isHidden: false
 forumTopicId: 301616
 ---
 

curriculum/challenges/english/08-coding-interview-prep/algorithms/inventory-update.english.md

@@ -2,6 +2,7 @@
 id: a56138aff60341a09ed6c480
 title: Inventory Update
 challengeType: 5
+isHidden: false
 forumTopicId: 16019
 ---
 

curriculum/challenges/english/08-coding-interview-prep/algorithms/no-repeats-please.english.md

@@ -2,6 +2,7 @@
 id: a7bf700cd123b9a54eef01d5
 title: No Repeats Please
 challengeType: 5
+isHidden: false
 forumTopicId: 16037
 ---
 

curriculum/challenges/english/08-coding-interview-prep/algorithms/pairwise.english.md

@@ -2,6 +2,7 @@
 id: a3f503de51cfab748ff001aa
 title: Pairwise
 challengeType: 5
+isHidden: false
 forumTopicId: 301617
 ---