Remove stale near-duplicate version parser

The DEP_OPENSSL_LIBRESSL_VERSION_NUMBER handling has two near-duplicate
parsers. The new one added in 4ecaf69 was subsequently extended and the
old one went stale: libressl250, 310, 370, 380 are missing from it.

openssl/build.rs

@@ -111,60 +111,4 @@ fn main() {
             println!("cargo:rustc-cfg=ossl320");
         }
     }
-
-    if let Ok(version) = env::var("DEP_OPENSSL_LIBRESSL_VERSION_NUMBER") {
-        let version = u64::from_str_radix(&version, 16).unwrap();
-
-        if version >= 0x2_05_01_00_0 {
-            println!("cargo:rustc-cfg=libressl251");
-        }
-
-        if version >= 0x2_06_01_00_0 {
-            println!("cargo:rustc-cfg=libressl261");
-        }
-
-        if version >= 0x2_07_00_00_0 {
-            println!("cargo:rustc-cfg=libressl270");
-        }
-
-        if version >= 0x2_07_01_00_0 {
-            println!("cargo:rustc-cfg=libressl271");
-        }
-
-        if version >= 0x2_07_03_00_0 {
-            println!("cargo:rustc-cfg=libressl273");
-        }
-
-        if version >= 0x2_08_00_00_0 {
-            println!("cargo:rustc-cfg=libressl280");
-        }
-
-        if version >= 0x2_09_01_00_0 {
-            println!("cargo:rustc-cfg=libressl291");
-        }
-
-        if version >= 0x3_02_01_00_0 {
-            println!("cargo:rustc-cfg=libressl321");
-        }
-
-        if version >= 0x3_03_02_00_0 {
-            println!("cargo:rustc-cfg=libressl332");
-        }
-
-        if version >= 0x3_04_00_00_0 {
-            println!("cargo:rustc-cfg=libressl340");
-        }
-
-        if version >= 0x3_05_00_00_0 {
-            println!("cargo:rustc-cfg=libressl350");
-        }
-
-        if version >= 0x3_06_00_00_0 {
-            println!("cargo:rustc-cfg=libressl360");
-        }
-
-        if version >= 0x3_06_01_00_0 {
-            println!("cargo:rustc-cfg=libressl361");
-        }
-    }
 }