pip compile: exclude --upgrade-package from the header (#5032)

## Summary

Fixes #5031.

## Test Plan

Existing snapshot tests should cover it.

crates/uv/src/commands/pip/compile.rs

@@ -547,6 +547,12 @@ fn cmd(
                 return Some(None);
             }
 
+            // Always skip the `--upgrade-package` flag, and mark the next item as skipped
+            if arg == "--upgrade-package" || arg == "-P" {
+                *skip_next = Some(true);
+                return Some(None);
+            }
+
             // Always skip the `--quiet` flag.
             if arg == "--quiet" || arg == "-q" {
                 *skip_next = None;

crates/uv/tests/pip_compile.rs

@@ -4748,7 +4748,7 @@ fn upgrade_package() -> Result<()> {
     exit_code: 0
     ----- stdout -----
     # This file was autogenerated by uv via the following command:
-    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --output-file requirements.txt --upgrade-package click
+    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --output-file requirements.txt
     black==23.10.1
         # via -r requirements.in
     click==8.1.7
@@ -4794,7 +4794,7 @@ fn upgrade_constraint() -> Result<()> {
     exit_code: 0
     ----- stdout -----
     # This file was autogenerated by uv via the following command:
-    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --output-file requirements.txt --upgrade-package iniconfig<2
+    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --output-file requirements.txt
     iniconfig==1.1.1
         # via -r requirements.in
 
@@ -4813,7 +4813,7 @@ fn upgrade_constraint() -> Result<()> {
     exit_code: 0
     ----- stdout -----
     # This file was autogenerated by uv via the following command:
-    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --output-file requirements.txt --upgrade-package iniconfig
+    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --output-file requirements.txt
     iniconfig==2.0.0
         # via -r requirements.in