Remove erroneously added Lab theme from plugin repo

.gitmodules

@@ -127,6 +127,3 @@
 [submodule "bootstrap-rst"]
 	path = bootstrap-rst
 	url = https://github.com/Alexqw/bootstrap-rst
-[submodule "lab"]
-	path = lab
-	url = https://github.com/mothsART/pelican-lab

lab

@@ -1 +0,0 @@
-Subproject commit d37e55e7aa6755fe6f587bcc243b9b27e4d23aba