Remove out-of-date comments about ICU4C.

There are comments about ICU4C using wrong timezone data spread
throughout the relevant code. These comments are now no longer
applicable, for two major reasons:

- ICU (both ICU4C and ICU4J) now uses timezone data that is in sync with
  the rest of the system. A fact that's even explicitly tested in a CTS
  test.
- The relevant ICU4C calls no longer generate GMT+XX:XX strings, but
  only return time zone names when present, so ICU4C generating them
  wrong is no longer an issue.

Test: m checkbuild
Change-Id: I361d2317d08b70461b3d1d019427005267e36269
2 files changed