Use full Python version when determining compatibility (#528)

## Summary

When resolving with Python 3.7.13, I was failing to find a matching
distribution that required Python 3.7.9 or later.

crates/puffin-cli/tests/snapshots/venv__create_venv.snap

@@ -4,7 +4,7 @@ info:
   program: puffin
   args:
     - venv
-    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmprOsp0M/.venv
+    - /var/folders/nt/6gf2v7_s3k13zq_t3944rwz40000gn/T/.tmpINXhJh/.venv
     - "--python"
     - python3.12
 ---
@@ -13,6 +13,6 @@ exit_code: 0
 ----- stdout -----
 
 ----- stderr -----
-Using Python 3.11 at [PATH]
+Using Python [VERSION] at [PATH]
 Creating virtual environment at: /home/ferris/project/.venv
 

crates/puffin-cli/tests/snapshots/venv__create_venv_defaults_to_cwd.snap

@@ -12,6 +12,6 @@ exit_code: 0
 ----- stdout -----
 
 ----- stderr -----
-Using Python 3.11 at [PATH]
+Using Python [VERSION] at [PATH]
 Creating virtual environment at: .venv
 

crates/puffin-cli/tests/venv.rs

@@ -18,7 +18,7 @@ fn create_venv() -> Result<()> {
 
     insta::with_settings!({
         filters => vec![
-            (r"Using Python 3.12 at .+", "Using Python 3.11 at [PATH]"),
+            (r"Using Python 3\.\d+\.\d+ at .+", "Using Python [VERSION] at [PATH]"),
             (temp_dir.to_str().unwrap(), "/home/ferris/project"),
         ]
     }, {
@@ -42,7 +42,7 @@ fn create_venv_defaults_to_cwd() -> Result<()> {
 
     insta::with_settings!({
         filters => vec![
-            (r"Using Python 3.12 at .+", "Using Python 3.11 at [PATH]"),
+            (r"Using Python 3\.\d+\.\d+ at .+", "Using Python [VERSION] at [PATH]"),
             (temp_dir.to_str().unwrap(), "/home/ferris/project"),
         ]
     }, {