"core": Get rid of "/..."-BlessingPatterns.

This is Part 3 of the plan described in
https://vanadium-review.googlesource.com/#/c/1757/

MultiPart: 1/3
Change-Id: I75dbf8c1b1f6d8953f09370bcb1af8795947a901
diff --git a/security/principal_test.go b/security/principal_test.go
index 3b3100c..99e512f 100644
--- a/security/principal_test.go
+++ b/security/principal_test.go
@@ -158,7 +158,7 @@
 	}{
 		{
 			matched: []security.Blessings{aliceworkfriend, aliceworkboss},
-			pattern: "alice/work/...",
+			pattern: "alice/work",
 		},
 		{
 			matched: []security.Blessings{aliceworkfriend},
@@ -170,15 +170,15 @@
 		},
 		{
 			matched: []security.Blessings{aliceworkfriend, alicegymfriend, aliceworkboss},
-			pattern: "alice/...",
+			pattern: "alice",
 		},
 		{
 			matched: []security.Blessings{aliceworkfriend, alicegymfriend, aliceworkboss},
-			pattern: "...",
+			pattern: security.AllPrincipals,
 		},
 		{
 			matched: nil,
-			pattern: "alice/school/...",
+			pattern: "alice/school",
 		},
 	}