libevent: remove autotools build deps again (#42908)

The deps were added in #40945 to make it work on macOS 11, because the
old configure scripts only detect macOS 10. Apparently people reported the
autoreconf script caused issues, later fixed in #41057. However, also
with that fix, things are incorrect, cause people now report:

```
libtool: You should recreate aclocal.m4 with macros from libtool 2.4.7
libtool: and run autoconf again.
```

HOWEVER, all this is unnecessary, because the underlying issue was
already fixed long ago, it's just that it regressed at some point, but
it's back in place since #41205.

var/spack/repos/builtin/packages/libevent/package.py

@@ -43,10 +43,6 @@ class Libevent(AutotoolsPackage):
     depends_on("openssl@:1.0", when="@:2.0+openssl")
     depends_on("openssl", when="+openssl")
 
-    depends_on("autoconf", type="build")
-    depends_on("automake", type="build")
-    depends_on("libtool", type="build")
-
     def url_for_version(self, version):
         if version >= Version("2.0.22"):
             url = "https://github.com/libevent/libevent/releases/download/release-{0}-stable/libevent-{0}-stable.tar.gz"
@@ -60,9 +56,6 @@ def libs(self):
         libs = find_libraries("libevent", root=self.prefix, shared=True, recursive=True)
         return LibraryList(libs)
 
-    def autoreconf(self, spec, prefix):
-        autoreconf("--force", "--install", "--symlink")
-
     def configure_args(self):
         spec = self.spec
         configure_args = []