Remove nightly toolchain from contracts and nightly build

Building with the beta toolchain should be enough to alert us to
impending compiler and clippy changes.

.github/workflows/ci-contracts-matrix-includes.json

@@ -6,9 +6,5 @@
   {
     "rust":"beta",
     "runOnEvent":"pull_request"
-  },
-  {
-    "rust":"nightly",
-    "runOnEvent":"pull_request"
   }
-]
+]

.github/workflows/ci-contracts.yml

@@ -27,7 +27,6 @@ jobs:
     # since it's going to be compiled into wasm, there's absolutely
     # no point in running CI on different OS-es
     runs-on: ubuntu-20.04
-    continue-on-error: ${{ matrix.rust == 'nightly' }}
     needs: matrix_prep
     strategy:
       fail-fast: false
@@ -61,7 +60,6 @@ jobs:
           args: --manifest-path contracts/Cargo.toml --all -- --check
 
       - uses: actions-rs/cargo@v1
-        if: ${{ matrix.rust != 'nightly' }}
         with:
           command: clippy
           args: --lib --manifest-path contracts/Cargo.toml --workspace --all-targets -- -D warnings

.github/workflows/nightly_build.yml

@@ -21,7 +21,7 @@ jobs:
     strategy:
       matrix: ${{fromJson(needs.matrix_prep.outputs.matrix)}}
     runs-on: ${{ matrix.os }}
-    continue-on-error: ${{ matrix.rust == 'nightly' || matrix.rust == 'beta' || matrix.rust == 'stable' }}
+    continue-on-error: ${{ matrix.rust == 'beta' || matrix.rust == 'stable' }}
     steps:
       - name: Install Dependencies (Linux)
         run: sudo apt-get update && sudo apt-get install libwebkit2gtk-4.0-dev build-essential curl wget libssl-dev libgtk-3-dev libudev-dev squashfs-tools protobuf-compiler

.github/workflows/nightly_build_matrix_includes.json

@@ -30,21 +30,5 @@
     "os":"custom-runner-mac-m1",
     "rust":"beta",
     "runOnEvent":"schedule"
-  },
-
-  {
-    "os":"custom-linux",
-    "rust":"nightly",
-    "runOnEvent":"schedule"
-  },
-  {
-    "os":"windows10",
-    "rust":"nightly",
-    "runOnEvent":"schedule"
-  },
-  {
-    "os":"custom-runner-mac-m1",
-    "rust":"nightly",
-    "runOnEvent":"schedule"
   }
 ]