Run the font/Fluent linter tests if their Python requirements change

The `requirements.txt` files of the two Python-based workflows were not
included in the file-based allowlist, which prevented the font/Fluent
linter tests from running if their contents changed. This commit fixes
that oversight from the original introduction of the workflows.

.github/workflows/fluent_linter.yml

@@ -4,6 +4,7 @@ on:
     paths:
       - 'l10n/en-US/**.ftl'
       - '.github/fluent_linter_config.yml'
+      - '.github/fluent_linter_requirements.txt'
       - '.github/workflows/fluent_linter.yml'
     branches:
       - master
@@ -11,6 +12,7 @@ on:
     paths:
       - 'l10n/en-US/**.ftl'
       - '.github/fluent_linter_config.yml'
+      - '.github/fluent_linter_requirements.txt'
       - '.github/workflows/fluent_linter.yml'
     branches:
       - master

.github/workflows/font_tests.yml

@@ -8,6 +8,7 @@ on:
       - 'src/**'
       - 'test/test.mjs'
       - 'test/font/**'
+      - '.github/font_tests_requirements.txt'
       - '.github/workflows/font_tests.yml'
     branches:
       - master
@@ -19,6 +20,7 @@ on:
       - 'src/**'
       - 'test/test.mjs'
       - 'test/font/**'
+      - '.github/font_tests_requirements.txt'
       - '.github/workflows/font_tests.yml'
     branches:
       - master