Merge rust-bitcoin/rust-bitcoin#2112: ci: fuzz test YAML toolchain future-proof

3e6021bbc6 ci: fuzz test YAML toolchain future-proof (Einherjar)

Pull request description:

  To avoid YAML automatic parsing of inputs as floats, e.g. [`1.60` being parsed as `1.6`](https://github.com/rust-bitcoin/rust-bitcoin/pull/2109#issuecomment-1751392327), it is best to future-proof the `toolchain` input in CI fuzz testing as a string.

ACKs for top commit:
  vincenzopalazzo:
    ACK 3e6021bbc6
  apoelstra:
    ACK 3e6021bbc6
  tcharding:
    ACK 3e6021bbc6

Tree-SHA512: 838afb401fcfbb00717d6d3efff013cda08dabe4962ee0e914c3cf438a5cc8e83fa336dbd920b299fe95f935c0c1d76cf15d3f6fc6f763ea15a1746e7254d94f

.github/workflows/fuzz.yml

@@ -49,7 +49,7 @@ hashes_sha1,
           key: cache-${{ matrix.target }}-${{ hashFiles('**/Cargo.toml','**/Cargo.lock') }}
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.65.0
+          toolchain: "1.65.0"
           override: true
           profile: minimal
       - name: fuzz