libkcapi: fix quoting error found by dxpb

In sh, if you set a variable like:
depends=abcdef>=ghi_jkl
then you will get a file: =ghi_jkl in the current working directory.

This suggests the >= requirement was never enforced for this
package, but now it can be.

To replicate this problem: << EOF
./xbps-src show-pkg-var libkcapi-devel
depends
EOF

srcpkgs/libkcapi/template

@@ -25,7 +25,7 @@ post_install() {
 }
 
 libkcapi-devel_package() {
-	depends=${sourcepkg}>=${version}_${revision}
+	depends="${sourcepkg}>=${version}_${revision}"
 	short_desc+=" - Development files"
 	pkg_install() {
 		vmove usr/include