move back to pure upstream version (#50)

.gitmodules

@@ -1,4 +1,4 @@
 [submodule "secp256k1_wrapper/secp256k1"]
 	path = vendor/secp256k1
-	url = https://github.com/status-im/secp256k1.git
+	url = https://github.com/bitcoin-core/secp256k1.git
 	branch = master

ci/Jenkinsfile

@@ -34,25 +34,21 @@ pipeline {
       }
     }
 
-    stage('Tests') {
-      parallel {
-        stage('C') {
-          environment {
-            NIMLANG = 'c'
-          }
-          steps {
-            sh 'nimble test'
-          }
-        }
+    stage('Tests: C') {
+      environment {
+        NIMLANG = 'c'
+      }
+      steps {
+        sh 'nimble test'
+      }
+    }
 
-        stage('C++') {
-          environment {
-            NIMLANG = 'cpp'
-          }
-          steps {
-            sh 'nimble test'
-          }
-        }
+    stage('Tests: C++') {
+      environment {
+        NIMLANG = 'cpp'
+      }
+      steps {
+        sh 'nimble test'
       }
     }
   }

vendor/secp256k1

@@ -1 +1 @@
-Subproject commit 1dd68bcd47b053673a34cd83490d79d787da1585
+Subproject commit 346a053d4c442e08191f075c3932d03140579d47