GitGraph: e2e tests, added commit IDs to test graphs

Followed practice of other tests so that commit IDs are
stabilised (i.e., not randomly generated) and therefore
don't show repeatedly in Cypress diff output screenshots

cypress/integration/rendering/gitGraph.spec.js

@@ -704,14 +704,14 @@ gitGraph TB:
   it('34: should render a simple gitgraph with two branches from same commit', () => {
     imgSnapshotTest(
       `gitGraph
-      commit
-      commit
+      commit id:"1-abcdefg"
+      commit id:"2-abcdefg"
       branch feature-001
-      commit
-      commit
+      commit id:"3-abcdefg"
+      commit id:"4-abcdefg"
       checkout main
       branch feature-002
-      commit
+      commit id:"5-abcdefg"
       checkout feature-001
       merge feature-002
       `,
@@ -721,14 +721,14 @@ gitGraph TB:
   it('35: should render a simple gitgraph with two branches from same commit | Vertical Branch', () => {
     imgSnapshotTest(
       `gitGraph TB:
-      commit
-      commit
+      commit id:"1-abcdefg"
+      commit id:"2-abcdefg"
       branch feature-001
-      commit
-      commit
+      commit id:"3-abcdefg"
+      commit id:"4-abcdefg"
       checkout main
       branch feature-002
-      commit
+      commit id:"5-abcdefg"
       checkout feature-001
       merge feature-002
       `,