build: Drop deprecrated ACLOCAL_AMFLAGS

In parallel with tpm2-software/tpm2-tss#2952

Signed-off-by: Christopher Byrne <salah.coronya@gmail.com>

Author: salahcoronya

Makefile.am

@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: BSD-2-Clause
 # we have BUILT_SOURCES so builddir must be in VPATH
 VPATH = $(srcdir) $(builddir)
-ACLOCAL_AMFLAGS = -I m4 --install
 
 .PHONY: unit-count