fix(ec): drop comments the ECCodes generator cannot parse - #533

The Flatpak job regenerates ECCodes.h from ECCodes.abstract rather than using
the committed header, and amule-project#530's comments in that file made the generated
header unparseable — "invalid preprocessing directive #=" and a truncated
ECOpCodes enum, failing every Flatpak build on master.

Two separate ways those comments broke it:

- The generator only skips a line as a comment when it matches "^#", i.e. with
  no leading whitespace. The comments inside the tag section were indented to
  line up with the entries, so they fell through to the data path, lost their
  leading tab and had every word turned into a field.
- It also flattens the file into a CMake list by replacing newlines with ";"
  (abstracts/CMakeLists.txt), so a semicolon inside a comment splits the line
  and the fragment after it no longer starts with "#" — which is where the
  mangled ECOpCodes entry came from.

Documentation for these codes already lives in the hand-maintained ECCodes.h,
so the fix is simply to keep the abstract to entries. Verified by generating a
header from the abstract before and after: master's produces 8 mangled lines
and 11 compile errors, this produces none, with all seven new codes present.