Make the sentinel const instead of changing the C analyzer.

Author: ZeroIntensity

Python/pystate.c

@@ -3484,7 +3484,7 @@ PyInterpreterView_FromMain(void)
 // thread state was attached.
 // To do this, we just use the memory address of a global variable and
 // cast it to a PyThreadState *.
-static int NO_TSTATE_SENTINEL = 0;
+static const int NO_TSTATE_SENTINEL = 0;
 
 PyThreadState *
 PyThreadState_Ensure(PyInterpreterGuard *guard)

Tools/c-analyzer/cpython/ignored.tsv

@@ -198,9 +198,6 @@ Python/pystate.c	-	_Py_tss_tstate	-
 Python/pystate.c	-	_Py_tss_gilstate	-
 Python/pystate.c	-	_Py_tss_interp	-
 
-# Global sentinel that is fine to share across interpreters
-Python/pystate.c  - NO_TSTATE_SENTINEL -
-
 ##-----------------------
 ## should be const
 # XXX Make them const.