chore: fix typo in README (#970)

Co-authored-by: Lucio Franco <[email protected]>

README.md

@@ -61,8 +61,8 @@ possible.
 
 With `prost-build` v0.11 release, `protoc` will be required to invoke
 `compile_protos` (unless `skip_protoc` is enabled). Prost will no longer provide
-bundled a `protoc` or attempt to compile `protoc` for users. For install
-instructions for `protoc` please check out the [protobuf install] instructions.
+bundled `protoc` or attempt to compile `protoc` for users. For install
+instructions for `protoc`, please check out the [protobuf install] instructions.
 
 [protobuf install]: https://github.com/protocolbuffers/protobuf#protobuf-compiler-installation