Fix typo in travis CI and remove allow_failure

.travis.yml

@@ -33,9 +33,6 @@ env:
 
 allow_failures:
   matrix:
-    # no musl gcc
-    - ARCH="x86_64" SRC="biscuit"
-    - ARCH="aarch64" SRC="biscuit"
     # too slow or homebrew too old
     - os: osx
 
@@ -56,7 +53,7 @@ install:
     sudo apt update;
     sudo apt install linux-headers-$(uname -r);
     wget https://musl.cc/aarch64-linux-musl-cross.tgz;
-    tar -xvf aarc64-linux-musl-cross.tgz;
+    tar -xvf aarch64-linux-musl-cross.tgz;
     export PATH=$PATH:$PWD/aarch64-linux-musl-cross/bin;
     elif [ $TRAVIS_OS_NAME = osx ]; then
     brew tap SergioBenitez/osxct;