src: fix minor typo in comments

Correcting a couple of minor spelling typos in comments.

PR-URL: nodejs#8736
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>

src/node_contextify.cc

@@ -351,7 +351,7 @@ class ContextifyContext {
     ContextifyContext* ctx;
     ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());
 
-    // Stil initializing
+    // Still initializing
     if (ctx->context_.IsEmpty())
       return;
 
@@ -381,7 +381,7 @@ class ContextifyContext {
     ContextifyContext* ctx;
     ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());
 
-    // Stil initializing
+    // Still initializing
     if (ctx->context_.IsEmpty())
       return;
 
@@ -407,7 +407,7 @@ class ContextifyContext {
     ContextifyContext* ctx;
     ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());
 
-    // Stil initializing
+    // Still initializing
     if (ctx->context_.IsEmpty())
       return;
 
@@ -434,7 +434,7 @@ class ContextifyContext {
     ContextifyContext* ctx;
     ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());
 
-    // Stil initializing
+    // Still initializing
     if (ctx->context_.IsEmpty())
       return;
 
@@ -450,7 +450,7 @@ class ContextifyContext {
     ContextifyContext* ctx;
     ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());
 
-    // Stil initializing
+    // Still initializing
     if (ctx->context_.IsEmpty())
       return;