MariaDB: remove useless dependency on Bison when building the 10.2.5 version

This is a follow-up of commit 8f032e6d:
Bison is only required when building from the repository.

component/mariadb/mariarocks.cfg

@@ -11,4 +11,3 @@ configure-options +=
   -DCMAKE_C_COMPILER=${gcc:location}/bin/gcc
   -DCMAKE_CXX_COMPILER=${gcc:location}/bin/g++
   -DCMAKE_INSTALL_RPATH=${gcc:location}/lib:${gcc:location}/lib64:${:CMAKE_INSTALL_RPATH}
-  -DCMAKE_PROGRAM_PATH=${bison:location}/bin

software/neoppod/software-myrocks-dev.cfg

 [buildout]
 extends =
-    ../../component/bison/buildout.cfg
     software.cfg
     ../../component/mariadb/mariarocks.cfg