Removed submodule HTG_2021

Author: Celina Lin

.gitmodules

@@ -155,9 +155,6 @@
 [submodule "RNA_2021"]
 	path = RNA_2021
 	url = https://github.com/bioinformatics-ca/RNA_2021.git
-[submodule "HTG_2021"]
-	path = HTG_2021
-	url = https://github.com/bioinformatics-ca/HTG_2021.git
 [submodule "IDE_2021"]
 	path = IDE_2021
 	url = https://github.com/bioinformatics-ca/IDE_2021.git