Remove reference to specific rustc version

Author: rcvalle

src/doc/rustc/src/exploit-mitigations.md

@@ -29,9 +29,7 @@ to document these exploit mitigations and how they apply to Rust.
 This section documents the exploit mitigations applicable to the Rust
 compiler when building programs for the Linux operating system on the AMD64
 architecture and equivalent.<sup id="fnref:1" role="doc-noteref"><a
-href="#fn:1" class="footnote">1</a></sup> All examples in this section were
-built using the Rust compiler version 1.40.0 (2019-12-19) on Debian testing
-(Bullseye).
+href="#fn:1" class="footnote">1</a></sup>
 
 The Rust Programming Language currently has no specification. The Rust
 compiler (i.e., rustc) is the language reference implementation. All