Raise MSRV to 1.51.1

In 8273b80 we (I) added a dep on `hex` which silently raised the MSRV
of this branch to Rust 1.51.1

Because of how we test on this branch this was not caught by CI. The
version with this change has been released for 2 years now and no-one
has complained implying that no-one is building with Rust 1.41

Although it is a violation of semver, lets just bump the MSRV in a
point release and live with the mistake.

Author: tcharding

README.md

@@ -76,14 +76,7 @@ For more information please see `./CONTRIBUTING.md`.
 
 ## Minimum Supported Rust Version (MSRV)
 
-This library should always compile with any combination of features (minus
-`no-std`) on **Rust 1.41.1** or **Rust 1.47** with `no-std`.
-
-To build with the MSRV you will need to pin some dependencies (also for `no-std`):
-```
-cargo update -p serde --precise 1.0.156
-cargo update -p syn --precise 1.0.107
-```
+This library should always compile with any combination of features on **Rust 1.51.1**.
 
 ## Installing Rust
 

bitcoin/CHANGELOG.md

@@ -1,3 +1,11 @@
+# 0.30.3 - 2025-12-01
+
+- Bump the MSRV to Rust 1.51.1
+
+Sorry, we accidentally did this 2 years ago in 0.30.2, since no-one
+complained we decided to keep it even though it is a semver violation.
+If you need to build with Rust 1.41 please pin to `v0.30.1`.
+
 # 0.30.2 - 2023-11-16
 
 - Expose valid (min, max) difficulty transition thresholds [#1820](Expose valid (min, max) difficulty transition thresholds)

bitcoin/contrib/test.sh

@@ -23,22 +23,6 @@ if cargo --version | grep beta; then
     STABLE=false
 fi
 
-# Pin dependencies as required if we are using MSRV toolchain.
-if cargo --version | grep "1\.41"; then
-    cargo update -p cc --precise 1.0.77
-    # 1.0.157 uses syn 2.0 which requires edition 2018
-    cargo update -p serde --precise 1.0.156
-
-    # latest arrayvec build fails because of `track_caller`.
-    cargo update -p arrayvec --precise 0.7.2
-fi
-
-# Pin dependencies as above (required for no-std tests that use Rust 1.47 toolchain).
-if cargo --version | grep "1\.47"; then
-    cargo update -p serde --precise 1.0.156
-    cargo update -p syn --precise 1.0.107
-fi
-
 # We should not have any duplicate dependencies. This catches mistakes made upgrading dependencies
 # in one crate and not in another (e.g. upgrade bitcoin_hashes in bitcoin but not in secp).
 duplicate_dependencies=$(