chore: update toolchain in CI

Author: ramonfmir

.github/workflows/docs.yml

@@ -23,7 +23,7 @@ jobs:
         run: |
           set -o pipefail
           curl -sSfL https://github.com/leanprover/elan/releases/download/v3.0.0/elan-x86_64-unknown-linux-gnu.tar.gz | tar xz
-          ./elan-init -y --default-toolchain leanprover/lean4:v4.4.0-rc1
+          ./elan-init -y --default-toolchain leanprover/lean4:v4.6.0-rc1
           echo "$HOME/.elan/bin" >> $GITHUB_PATH
       - name: Install Rust and Cargo
         run: |
@@ -39,7 +39,7 @@ jobs:
           # Taken from https://github.com/leanprover-community/mathlib4_docs
 
           # Workaround for the lake issue
-          elan default leanprover/lean4:nightly
+          elan default leanprover/lean4:v4.6.0-rc1
           lake new workaround
           cd workaround
           cp -f ../mathlib4/lean-toolchain .

.github/workflows/main.yml

@@ -27,7 +27,7 @@ jobs:
         run: |
           set -o pipefail
           curl -sSfL https://github.com/leanprover/elan/releases/download/v3.0.0/elan-x86_64-unknown-linux-gnu.tar.gz | tar xz
-          ./elan-init -y --default-toolchain leanprover/lean4:v4.4.0-rc1
+          ./elan-init -y --default-toolchain leanprover/lean4:v4.6.0-rc1
           echo "$HOME/.elan/bin" >> $GITHUB_PATH
       - name: Install Rust and Cargo
         run: |