bazel overlay: fix regression to "list of string" bpdocs type.

A recent change to Blueprint [1] added the feature to infer the type of
list elements to more than just "list of strings", but this also changed
the text to "list of string" (without s). This CL fixes the bazel
overlay, which uses "list of strings".

Test: m bazel_overlay && bazel query //...  --package_path=out/soong/bazel_overlay

[1]: https://android.googlesource.com/platform/build/blueprint/+/764a77191737d68820082af40cf5ddc98dd264a3%5E%21/#F1

Change-Id: I7522d15b1ce751807e1881ce1e94f068d226b316
diff --git a/cmd/soong_build/bazel_overlay.go b/cmd/soong_build/bazel_overlay.go
index cdc5775..fc1b492 100644
--- a/cmd/soong_build/bazel_overlay.go
+++ b/cmd/soong_build/bazel_overlay.go
@@ -370,7 +370,7 @@
 
 		// Canonicalize and normalize module property types to Bazel attribute types
 		starlarkAttrType := prop.Type
-		if starlarkAttrType == "list of strings" {
+		if starlarkAttrType == "list of string" {
 			starlarkAttrType = "string_list"
 		} else if starlarkAttrType == "int64" {
 			starlarkAttrType = "int"