[vpython] Fix PEP425 naming.

vpython/api/vpython/spec.proto

Index: vpython/api/vpython/spec.proto
diff --git a/vpython/api/vpython/spec.proto b/vpython/api/vpython/spec.proto
index ddc366c4b036c64932b5ba2278c119f7ef0cff74..05181867d882332835884e0eacb87efd2174ef8f 100644
--- a/vpython/api/vpython/spec.proto
+++ b/vpython/api/vpython/spec.proto
@@ -49,7 +49,7 @@ message Spec {
     // (partial), that field will not be considered. For example, if a match
     // tag specifies just an ABI field, any system PEP425 tag with that ABI will
     // be considered a successful match, regardless of other field values.
-    repeated vpython.Pep425Tag match_tag = 3;
+    repeated vpython.PEP425Tag match_tag = 3;
   }
   repeated Package wheel = 2;
 
@@ -65,5 +65,5 @@ message Spec {
   // environment parameters. However, a given specification may offer its own
   // set of PEP425 tags representing the systems that it wants to be verified
   // against.
-  repeated vpython.Pep425Tag verify_pep425_tag = 4;
+  repeated vpython.PEP425Tag verify_pep425_tag = 4;
 }