8058180: .hgignore should be updated with webrev in all repos

Reviewed-by: jrose, katleman, jjg
diff --git a/hotspot/.hgignore b/hotspot/.hgignore
index c652de1..e9ce602 100644
--- a/hotspot/.hgignore
+++ b/hotspot/.hgignore
@@ -1,5 +1,6 @@
 ^build/
 ^dist/
+^webrev
 /nbproject/private/
 ^src/share/tools/hsdis/build/
 ^src/share/tools/IdealGraphVisualizer/[a-zA-Z0-9]*/build/