Google::Protobuf::Map#inspect should be consistent with Hash#inspect

ruby/ext/google/protobuf_c/map.c

diff --git a/ruby/ext/google/protobuf_c/map.c b/ruby/ext/google/protobuf_c/map.c
index 4ee71d1..12e7a9d 100644
--- a/ruby/ext/google/protobuf_c/map.c
+++ b/ruby/ext/google/protobuf_c/map.c
@@ -683,7 +683,7 @@
       first = false;
     }
     str = rb_str_append(str, rb_funcall(key, inspect_sym, 0));
-    str = rb_str_cat2(str, " => ");
+    str = rb_str_cat2(str, "=>");
     str = rb_str_append(str, rb_funcall(value, inspect_sym, 0));
   }