gitian: bump descriptors for master

Tree-SHA512: dc56ab285ea3fd293794341d7e2f8452730d3efb59f793112d4e1b036a051f9d221a7e577a460b426ecfb1578558203fa6a432efc62e6cabc534059719a2b437

contrib/gitian-descriptors/gitian-linux.yml

@@ -1,5 +1,5 @@
 ---
-name: "bitcoin-linux-0.15"
+name: "bitcoin-linux-0.16"
 enable_cache: true
 suites:
 - "trusty"

contrib/gitian-descriptors/gitian-osx.yml

@@ -1,5 +1,5 @@
 ---
-name: "bitcoin-osx-0.15"
+name: "bitcoin-osx-0.16"
 enable_cache: true
 suites:
 - "trusty"

contrib/gitian-descriptors/gitian-win.yml

@@ -1,5 +1,5 @@
 ---
-name: "bitcoin-win-0.15"
+name: "bitcoin-win-0.16"
 enable_cache: true
 suites:
 - "trusty"