Remove all the `cpp_std: "experimental"`s.

None of them are necessary, and it's more intention-revealing to say
`c++2a` or whatever anyway.

Test: treehugger
Change-Id: Ie1df26499d160d6fc757d17fcb0121997bda14f9

init/Android.bp

@@ -74,7 +74,6 @@ init_host_sources = [
 
 cc_defaults {
     name: "init_defaults",
-    cpp_std: "experimental",
     sanitize: {
         misc_undefined: ["signed-integer-overflow"],
     },
@@ -336,7 +335,6 @@ genrule {
 cc_binary {
     name: "host_init_verifier",
     host_supported: true,
-    cpp_std: "experimental",
     cflags: [
         "-Wall",
         "-Wextra",

property_service/libpropertyinfoparser/Android.bp

@@ -8,7 +8,6 @@ cc_library_static {
     native_bridge_supported: true,
     srcs: ["property_info_parser.cpp"],
 
-    cpp_std: "experimental",
     cppflags: [
         "-Wall",
         "-Wextra",

property_service/libpropertyinfoserializer/Android.bp

@@ -1,7 +1,6 @@
 cc_defaults {
     name: "propertyinfoserializer_defaults",
     host_supported: true,
-    cpp_std: "experimental",
     cppflags: [
         "-Wall",
         "-Wextra",

property_service/property_info_checker/Android.bp

@@ -2,7 +2,6 @@ cc_binary {
     name: "property_info_checker",
     host_supported: true,
     static_executable: true,
-    cpp_std: "experimental",
     static_libs: [
         "libpropertyinfoserializer",
         "libpropertyinfoparser",

toolbox/Android.bp

@@ -19,7 +19,6 @@ genrule {
 cc_defaults {
     name: "toolbox_binary_defaults",
     defaults: ["toolbox_defaults"],
-    cpp_std: "experimental",
     srcs: [
         "toolbox.c",
         "getevent.c",