Fix error when get version using Wget

GitHub now returns lowercase:

wget -SqO /dev/null https://github.com/rancher/k3s/releases/latest |& grep -i location

  location: https://github.com/rancher/k3s/releases/tag/v1.17.3+k3s1

install.sh

@@ -307,7 +307,7 @@ get_release_version() {
                 VERSION_K3S=$(curl -w '%{url_effective}' -I -L -s -S ${GITHUB_URL}/latest -o /dev/null | sed -e 's|.*/||')
                 ;;
             wget)
-                VERSION_K3S=$(wget -SqO /dev/null ${GITHUB_URL}/latest 2>&1 | grep Location | sed -e 's|.*/||')
+                VERSION_K3S=$(wget -SqO /dev/null ${GITHUB_URL}/latest 2>&1 | grep -i Location | sed -e 's|.*/||')
                 ;;
             *)
                 fatal "Incorrect downloader executable '$DOWNLOADER'"

package/rpm/install.sh

@@ -354,7 +354,7 @@ get_release_version() {
                 VERSION_K3S=$(curl -w '%{url_effective}' -I -L -s -S ${GITHUB_URL}/latest -o /dev/null | sed -e 's|.*/||')
                 ;;
             wget)
-                VERSION_K3S=$(wget -SqO /dev/null ${GITHUB_URL}/latest 2>&1 | grep Location | sed -e 's|.*/||')
+                VERSION_K3S=$(wget -SqO /dev/null ${GITHUB_URL}/latest 2>&1 | grep -i Location | sed -e 's|.*/||')
                 ;;
             *)
                 fatal "Incorrect downloader executable '$DOWNLOADER'"