Remove build metadata from libgit2-sys dependency

Author: ehuss

Cargo.toml

@@ -57,7 +57,7 @@ jobserver = "0.1.26"
 lazy_static = "1.4.0"
 lazycell = "1.3.0"
 libc = "0.2.147"
-libgit2-sys = "0.15.2+1.6.4"
+libgit2-sys = "0.15.2"
 log = "0.4.19"
 memchr = "2.5.0"
 miow = "0.5.0"