x11/sirula: Unbreak build

Fix typo:
error: expected one of (, ., ::, ;, ?, }, or an operator, found :

--> /build/cargo-vendor-dir/osstrtools-0.2.2/src/lib.rs:754:42
 |

754 | unsafe { (bytes as *const _).cast:() }

|                                          ^ expected one of 7 possible tokens

error: could not compile osstrtools (lib) due to previous error

Typo was added in https://github.com/rabite0/osstrtools/commit/1179a979dbf22209547a74ce98d84745d1e54ef4

Approved by: portmgr (build fix blanket)