refactor(ocpp20): rewrite H9/H10/H11 + C10/C12 audit markers as descriptive comments...

refactor(ocpp20): rewrite H9/H10/H11 + C10/C12 audit markers as descriptive comments (issue #1936 l) (#1939)

Nine inline comments in OCPP20IncomingRequestService.ts (7) and its
sibling test file OCPP20IncomingRequestService-UpdateFirmware.test.ts
(2) carried internal audit-round finding numbers (H9, H10, H11, C10,
C12) as if they were code identifiers.

Production-file markers (7) originate from commit 3a6e89f634
'fix(ocpp20): remediate all OCPP 2.0.1 audit findings (#1726)' which
predates PR #1935. Test-file markers (2 H11) originate from commit
b50f9e5f 'refactor(tests): separate handler/listener tests and remove
setTimeout hacks' — same audit-round family, later commit.

The audit markers had the shape //<letter+><digits>[:-)] which is
distinct from the legitimate OCPP spec references elsewhere in the
repo (B11 - Reset, F06.FR.06, A02.FR.06, E05.FR.09, L01.FR.30,
C10.FR.04, C12.FR.05, ...) that all follow <UC>.FR.<NN>.

Each rewrite replaces the marker with a WHY-rationale or BDD-style
expectation describing the current-state behavior. See the PR body
table for the full before/after list.

Verification (POSIX character classes; portable across all git-grep -E
builds — the \s shorthand is a PCRE extension not supported by POSIX
ERE and silently returns no match on macOS git):

  git grep -inE '^[[:space:]]*//[[:space:]]*[A-Z]+[0-9]+[]:)-]' -- \
    src/ tests/

returns empty.

Comment-only change. No runtime behavior change.
Test invariant fail: 0, skipped: 6 holds.

Closes issue #1936 item (l).