ArmPlatformPkg: SpellCheck: Switch spellcheck CI to AuditOnly

ArmPlatformPkg: SpellCheck: Switch spellcheck CI to AuditOnly

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3445

Spellcheck was not covering all specified files due to CSpell v5 and
Node v10 incompatibility of current CI pipeline configuration.

This change switches the spellcheck for ArmPlatformPkg to AuditOnly to
avoid potentially numerous spell errors. The correction action is to be
revisited by package maintainers once the tool incompatibility is
resolved.

Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Signed-off-by: Sean Brogan <sean.brogan@microsoft.com>
Signed-off-by: Kun Qin <kuqin12@gmail.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>