remove unused themes

diff --git a/themes/hugo-bearblog b/themes/hugo-bearblog
deleted file mode 160000 (submodule)
index e43c252..0000000
--- a/themes/hugo-bearblog
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit e43c252b8dded99643a6217c516762c0049fe37d

diff --git a/themes/hugo-xmin b/themes/hugo-xmin
deleted file mode 160000 (submodule)
index c871e56..0000000
--- a/themes/hugo-xmin
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit c871e5665f5eceb919c8fdb284b73c7a07012646