Drop fabricated SET UP IDLE MODE TEXT qualifier decode; bump to 1.15.1

Spec verification against UICC_SPECS.md / TS 102 223 V18.3.0 §8.6
showed the Command Qualifier for SET UP IDLE MODE TEXT is RFU
("this byte is RFU") — no icon self-explanatory bit exists in any
generation (GSM 11.14 predates the command; TS 31.111 does not
override it). The v1.11.0 _idle_text_qualifier decoded bit 1 as
"icon self-explanatory" from an unverified source.

Remove the decoder; the command now uses generic RFU handling
(hidden at '00', raw hex otherwise). Tests updated accordingly.
Version 1.15.1, SW cache v21.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.backends._legacy:_Backend"
 
 [project]
 name = "simtrace2-pysniff"
-version = "1.15.0"
+version = "1.15.1"
 description = "Python-based sniffing tool for SIMtrace2 hardware (SIM card communication sniffer)"
 readme = {file = "README.md", content-type = "text/markdown"}
 license = {text = "GPL-2.0-or-later"}