Fix extra coma in README.md

Co-Authored-By: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/README.md b/README.md
index de1dd27..f868a0a 100644
--- a/README.md
+++ b/README.md
@@ -157,7 +157,7 @@
 
 #### Mbed TLS as a subproject
 
-Mbed TLS, supports being built as a CMake subproject. One can
+Mbed TLS supports being built as a CMake subproject. One can
 use `add_subdirectory()` from a parent CMake project to include Mbed TLS as a
 subproject.