Go back to Rust 1.61

as 1.65 makes the iOS build fail.

For Android, it would actually be enough to go back to 1.64, but let's
try what's needed for iOS.

.github/workflows/ci.yml

@@ -71,10 +71,10 @@ jobs:
         include:
           # Currently used Rust version, same as in `rust-toolchain` file.
           - os: ubuntu-latest
-            rust: 1.65.0
+            rust: 1.61.0
             python: 3.9
           - os: windows-latest
-            rust: 1.65.0
+            rust: 1.61.0
             python: false # Python bindings compilation on Windows is not supported.
 
           # Minimum Supported Rust Version = 1.61.0

rust-toolchain

@@ -1 +1 @@
-1.65.0
+1.61.0

scripts/coredeps/install-rust.sh

@@ -7,7 +7,7 @@ set -euo pipefail
 #
 # Avoid using rustup here as it depends on reading /proc/self/exe and
 # has problems running under QEMU.
-RUST_VERSION=1.65.0
+RUST_VERSION=1.61.0
 
 ARCH="$(uname -m)"
 test -f "/lib/libc.musl-$ARCH.so.1" && LIBC=musl || LIBC=gnu