fix: grpcio_tools not installed

At a first glance this seems like the corresponding pip package is not
installed, however this is not the case. To check for the protoc compiler
in the CMake file,`python3 -m grpc_tools.protoc' is called and
'Missing input file' is expected as the output. With any other output
the build will fail.

Due to a deprecation warning in pkg_resources Python package the output is different
from the expected, although the package is installed. There as been
a fix from Google, however it does only apply for Python verions >= 3.9
grpc/grpc@eae9c55

The implemented solution is to split the string into a list (after each \n) and
get the first element to retrieve the expected output. This will fix the
build, but the deprecation warnings are still printed

seerep_com/cmake/ProtobufGenerateGrpcPython.cmake

@@ -21,7 +21,21 @@ function(GRPC_GENERATE_PYTHON SRCS)
     ERROR_VARIABLE _pygrpc_output
   )
 
-  if(NOT (${_pygrpc_output} STREQUAL "Missing input file.\n"))
+  string(
+    REPLACE "\n"
+            ";"
+            _pygrpc_output
+            ${_pygrpc_output}
+  )
+
+  list(
+    GET
+    _pygrpc_output
+    0
+    _pygrpc_output
+  )
+
+  if(NOT (${_pygrpc_output} STREQUAL "Missing input file."))
     message(
       SEND_ERROR
         "Error: grpcio_tools not installed\ntry: sudo pip install grpcio_tools"