fix typo in nra_plugin.c #504

Job	Run time
ubuntu-latest\|debug\|--enable-mcsat\|CC=gcc CXX=g++	8m 47s
ubuntu-latest\|debug\|--enable-mcsat\|CC=clang CXX=clang++	9m 37s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=gcc CXX=g++	4m 19s
ubuntu-latest\|debug\|--enable-thread-safety\|CC=clang CXX=clang++	4m 57s
ubuntu-latest\|release\|--enable-mcsat\|CC=gcc CXX=g++	5m 36s
ubuntu-latest\|release\|--enable-mcsat\|CC=clang CXX=clang++	6m 23s
ubuntu-latest\|release\|--enable-thread-safety\|CC=gcc CXX=g++	2m 52s
ubuntu-latest\|release\|--enable-thread-safety\|CC=clang CXX=clang++	3m 11s
ubuntu-latest\|gcov\|--enable-mcsat\|CC=gcc CXX=g++	8m 36s
ubuntu-latest\|debug\|--enable-thread-safety --enable-mcsat\|CC=gcc CXX=g++	8m 35s
	1h 2m 53s

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