Now gnu11 is the default, bump experimental to gnu17.

Bug: http://b/232413369
Test: treehugger
Change-Id: I8a2b1eef744c219811c32ad46688437a1ba3f21e
diff --git a/bp2build/cc_library_conversion_test.go b/bp2build/cc_library_conversion_test.go
index 2775a10..ab92981 100644
--- a/bp2build/cc_library_conversion_test.go
+++ b/bp2build/cc_library_conversion_test.go
@@ -1914,9 +1914,9 @@
 		{cpp_std: "gnu++17", gnu_extensions: "true", bazel_cpp_std: "gnu++17"},
 
 		// some c_std test cases
-		{c_std: "experimental", gnu_extensions: "", bazel_c_std: "gnu11"},
-		{c_std: "experimental", gnu_extensions: "false", bazel_cpp_std: "c++17", bazel_c_std: "c11"},
-		{c_std: "experimental", gnu_extensions: "true", bazel_c_std: "gnu11"},
+		{c_std: "experimental", gnu_extensions: "", bazel_c_std: "gnu17"},
+		{c_std: "experimental", gnu_extensions: "false", bazel_cpp_std: "c++17", bazel_c_std: "c17"},
+		{c_std: "experimental", gnu_extensions: "true", bazel_c_std: "gnu17"},
 		{c_std: "gnu11", cpp_std: "gnu++17", gnu_extensions: "", bazel_cpp_std: "gnu++17", bazel_c_std: "gnu11"},
 		{c_std: "gnu11", cpp_std: "gnu++17", gnu_extensions: "false", bazel_cpp_std: "c++17", bazel_c_std: "c11"},
 		{c_std: "gnu11", cpp_std: "gnu++17", gnu_extensions: "true", bazel_cpp_std: "gnu++17", bazel_c_std: "gnu11"},