debian/control: Fix typo (package->Package)

Change-Id: Ia35c5dc603830b83670b20c3f45b6857cb9d19b4
dpkg-gencontrol: warning: package osmo-remsim-doc: unknown substitution variable ${misc:Package}
diff --git a/debian/control b/debian/control
index d161815..47033fb 100644
--- a/debian/control
+++ b/debian/control
@@ -90,7 +90,7 @@
  driver into pcscd.  This means you can use remote smart cards managed
  by osmo-remsim-server via normal PC/SC applications.
 
-package: osmo-remsim-doc
+Package: osmo-remsim-doc
 Architecture: all
 Section: doc
 Priority: optional