transpile: remove invalid Punct::new(' ') in fn convert_asm and update proc-macro2 (#1244)

`' '` is not a valid punctuation, and newer versions of `proc_macro2`
don't allow it. However, we don't seem to need the space here at all, as
`zstd` (from `c2rust-testsuite`) still transpiles and compiles
successfully without it.

This also updates to `proc-macro` `1.0.95` (from `1.0.86`) to test this.

#1243 should be able to be merged after this.

Author: kkysen

Cargo.lock

@@ -966,7 +966,6 @@ impl<'c> Translation<'c> {
             tokens.push(TokenTree::Punct(Punct::new(',', Alone)));
             let result = mk().call_expr(mk().ident_expr("out"), vec![mk().lit_expr(clobber)]);
             push_expr(&mut tokens, result);
-            tokens.push(TokenTree::Punct(Punct::new(' ', Alone)));
             push_expr(&mut tokens, mk().ident_expr("_"));
         }