Do not generate classpaths proto for RuntimeI18n apex.

This is historically significant jar that must be kept in boot image
and platform's classpath config. Setting generate_classpaths_proto to
false guarantees the latter.

Bug: 191127295
Test: atest CtsClasspathsTestCases
Change-Id: I68b41d54203af68d1b0a966632cf44639b95cfae
Merged-In: I68b41d54203af68d1b0a966632cf44639b95cfae