doc: Fix some misspellings

contrib/guix/manifest.scm

@@ -106,7 +106,7 @@ chain for " target " development."))
                                   (base-libc glibc-2.27)
                                   (base-gcc (make-gcc-rpath-link
                                              (make-ssp-fixed-gcc gcc-9))))
-  "Convienience wrapper around MAKE-CROSS-TOOLCHAIN with default values
+  "Convenience wrapper around MAKE-CROSS-TOOLCHAIN with default values
 desirable for building Bitcoin Core release binaries."
   (make-cross-toolchain target
                    base-gcc-for-libc