Eliminate Cargo.lock.msrv

We no longer need it since updating our MSRV to 1.56.1.

Issue #1809

Author: asomers

.cirrus.yml

@@ -56,7 +56,6 @@ task:
     - . $HOME/.cargo/env
     - rustup target add i686-unknown-freebsd
     - rustup component add --toolchain $TOOLCHAIN clippy
-    - cp Cargo.lock.msrv Cargo.lock
   << : *TEST
   i386_test_script:
     - . $HOME/.cargo/env
@@ -80,7 +79,6 @@ task:
     - sh rustup.sh -y --profile=minimal --default-toolchain $TOOLCHAIN
     - . $HOME/.cargo/env
     - rustup component add --toolchain $TOOLCHAIN clippy
-    - cp Cargo.lock.msrv Cargo.lock
   << : *TEST
   before_cache_script: rm -rf $CARGO_HOME/registry/index
 
@@ -134,7 +132,6 @@ task:
     - sh rustup.sh -y --profile=minimal --default-toolchain $TOOLCHAIN
     - . $HOME/.cargo/env
     - cargo install cross --version 0.2.1 # cross 0.2.2 bumped the MSRV to 1.58.1
-    - cp Cargo.lock.msrv Cargo.lock
   << : *TEST
   before_cache_script: rm -rf $CARGO_HOME/registry/index
 
@@ -160,7 +157,6 @@ task:
   setup_script:
     - rustup target add $TARGET
     - rustup component add clippy
-    - cp Cargo.lock.msrv Cargo.lock
   << : *TEST
   before_cache_script: rm -rf $CARGO_HOME/registry/index
 
@@ -249,7 +245,6 @@ task:
     - rustup target add $TARGET
     - rustup toolchain install $TOOLCHAIN --profile minimal --target $TARGET
     - rustup component add --toolchain $TOOLCHAIN clippy
-    - cp Cargo.lock.msrv Cargo.lock
   << : *BUILD
   before_cache_script: rm -rf $CARGO_HOME/registry/index